A University of Pennsylvania graduate student says a Starbucks barista in West Philadelphia mocked him for his stuttering disorder last week — just 29 days after the company closed its nearly 800 U.S. stores for anti-bias training following the wrongful arrests of two black men at a Center City store.

The 28-year-old student, who is pursuing a doctorate at the Wharton School, said he was shocked when he ordered an iced coffee at a Starbucks in University City, only to have the barista mimic his name by saying: "OK, S-S-Sam."

It was even more disturbing when he realized while walking back to his office that the barista had written his name on the cup as "SSSam."

"It's rare, as an adult, that that kind of disrespect happens," said Sam, who asked that his last name not be published because he feared being continually linked to the alleged bias. "It happens, but it's really rare to see it in print."

"Stuttering is an affliction that harms people every day," said Sam, who has had a stutter since age 6. "But I'm not the right person to be the face of that fight."

Starbucks regional vice president Camille Hymes reached out to Sam to learn more about what happened and to personally apologize, according to Reggie Borges, a Starbucks spokesperson.

"We are taking this incident seriously, and we have begun a full investigation," Borges said. "We have a zero-tolerance policy for any kind of discrimination. We don't  feel like this [discrimination] is reflective of our values or of our mission. We want everyone who comes to our stores to feel valued and to have a positive experience."

>> READ MORE: Starbucks gets recommendations on how to address bias. 

Sam confirmed that Hymes called him around 3 p.m. Monday.  "As someone who studies these kind of things [corporate decisions and operations], I believe she was sincere in her apology," he said.

At the time of the incident, just before 3 p.m. Wednesday at the store at 3401 Walnut St., Sam was not so much angry as shocked, he said.

"It felt rude," he said.

Initially, Sam reported the incident to Starbucks customer service via email and received a reply apologizing if he felt disrespected and offering him a $5 Starbucks credit.

"I thought it was kind of insulting," he said. "I also thought they didn't take my issue seriously. It was as if they give $5 to anyone who complains about anything.  I sort of got a generic email, and I didn't feel like I was heard."

Borges said Starbucks had learned a lot since it closed its stores for the afternoon of May 29 for employee anti-bias training following the April 12 arrests of Rashon Nelson and Donte Robinson, who were racially profiled while waiting to meet a third man in the store for a business meeting.

Starbucks later declined to pursue trespassing charges against the men, who were both 23 years old.  A video showing them being handcuffed and led out by police went viral and sparked protests and calls for boycotts all over the country.

>> READ MORE:  Starbucks closes stores for anti-racial bias training: Recap

>> READ MORE: Social media video shows arrests of black men at Philadelphia Starbucks -video

Sam usually goes to the Starbucks at 3901 Walnut, where he has always been treated with respect and courtesy, he said.  He doesn't plan to let what happened at the 34th and Walnut store affect his plans to buy coffee at the store at 39th and Walnut.

"I don't want to generalize one person's behavior," Sam said.  "I'm not going to impugn an entire organization because of one person."

>> READ MORE: Black men's arrests at Philadelphia Starbucks prompt city probes amid national outcry

Heather Grossman, director of the American Institute for Stuttering, an organization that provides speech therapy and counseling, said incidents like the one Sam described occur more often than most people realize.

"People are often very, very insensitive," Grossman said. "They don't realize that [stuttering] truly qualifies as a disability. They think it's a behavior." Or they treat it as if it's a temporary condition.

Stuttering is covered under the Americans With Disabilities Act, she said.

"But, unfortunately, there is still much blatant discrimination [including job discrimination] and way too many stories of people being mocked, dismissed, or imitated," Grossman later wrote in an email. Stuttering often is noticed in children between the ages of 2 and 6 when they are learning to form sentences.

Sam said he received speech therapy at the American Institute for Stuttering when he was a teenager.

Grossman said the mocking behavior Sam experienced tended to make people who stutter feel that their stuttering is something they should hide.

"And in the act of trying to hide their stutter, it causes a physical tension and avoidant behavior" that makes the stuttering only worse, she said.

"People don't realize that underneath in that person's soul is a lot of pain," Grossman said.

Sometimes people may give a different name when they encounter a server again in the hopes that perhaps they won't stutter, she said. Or they may pick a simpler drink to avoid pronouncing a difficult word, such as cappuccino or macchiato.

Tan Lekwijit, a fellow doctoral student at Wharton, first posted an account of the incident on Starbucks' Facebook page about 1:30 p.m. Sunday. The time stamp on the photo of the cup from the previous Wednesday showed the order was made at 2:53 p.m.

"My friend Sam who is a stutterer stuttered on his name when ordering a coffee at Starbucks. The barista said, "Okay, S-s-s-sam". When he received his coffee, he was shocked to see that his name on the cup was written as "SSSAM", which was disrespectful.

"I am writing this not because I want to get anybody into trouble, but because I want to raise awareness among the employees. There are many people with speech disorders who are in a worse position than my friend's and struggle with self-esteem and self-confidence. Getting this kind of treatment from people, especially service employees, only scars them— and I beg Starbucks employees to have this in mind."

Called about the posting, Lekwijit, 26, said: "I was angry, and I feel like no stutterer should be treated this way. Not just my friend, but for other people with speech disorders.

"I don't' know if the [bias] training they just had covered people with speech disabilities, but it should," Lekwijit said.

He also claimed his first Facebook post was deleted by Starbucks Sunday night about 9.  So he reposted it again on his own Facebook timeline later Sunday.

Borges, the Starbucks spokesperson,  said he's looking into whether someone deleted Lekwijit's original post. The Facebook page is supposed to serve as a platform for customers to give feedback to the company, he said:   "Normally, we wouldn't delete something like that."