I’ve got the Student Developer Pack and it includes one year hobbist account on Heroku.
It says that you need a credit card, but I don’t have one. How do I take upgrade the account if I don’t have a credit card ?
Write to the support of heroku, I think they may help you. If they won’t allow it, consider creating virtual card in application like Revolut, then your ordinary account wouldn’t be charged by accident.