It happened on Sunday when Brett Wolfe, 17, stopped at a Tim Hortons on Horton Street East and Wellington Street, in downtown London, Ont.
While inside, he started having breathing problems and asked to use the phone.
"They said, 'There's a payphone across the street.' Well, I said 'I need to call 911, I'm short of breath, I'm having an asthma attack' and they just ignored me."
Aldina King was with Wolfe when the attack happened.
She said it was clear her friend "needed hospital attention."
King said staff didn't act quickly.
"I didn't see any reaction, that's the funny thing about it, I didn't see any reaction. I sat there quietly dumbfounded."
A quick-thinking patron used a cellphone to call paramedics, but according to one report they weren't allowed to enter through an exit-only door.
Tim Hortons said the teen did ask to use the phone but didn't say he was in distress.
It was only when an employee went to get a manager that Wolfe indicated he was having trouble breathing.
A spokesperson said the manager knew paramedics had been called and that Wolfe walked outside on his own.
Tim Hortons said employees are encouraged to recognize signs of distress and call 911
In a statement sent to CBC News, the company said "our restaurants normally handle these unique situations right in the vast majority of cases. In this particular situation, this team member misjudged the circumstances."
It was also in a London, Ont., Tim Hortons that a cashier was fired five years ago when she gave a Timbit to a crying baby.
The cashier was later rehired.
Wolfe said he doesn't expect anything from the company, but he would like to see a change in attitude "and if something really does happen, they should let people call."
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