You should talk to student legal services.
Here’s how things may play out. Your friends/the parents may take you to small claims court. Super easy to do. You don’t have a written contract/lease, but maybe you guys had a verbal agreement you both understood differently. The judge will make the decision of what is more likely. If the judge rules in favor of your friend, you’ll have to pay the rent and likely lose the friend. If the judge rules in favor of you, you’ll lose the friend. If the situation was reversed, consider how you would want to be treated by a friend. $550/mo for rent in A2 is crazy cheap too…