Is it okay to rescind an accepted internship offer?

I wanted to ask if it's alright to withdraw an accepted internship offer. I had sent company A my company acceptance letter (university paperwork) and just returned to me recently. However, after accepting their offer (company A) I had received a better offer from company B which took them 2 weeks to contact me for an update. That is also why i accepted the company A in the first place because I thought company B had move on to other candidates.

From my interactions with company A, they had not provided me any formal offer letter from their side yet. Is it okay to revoke this acceptance? Are there any consequences if I do so? (I already had sent them an email about it awaiting for response). I know it's really dishonorable and kind of a jerk for not being able to make a final decision but I really liked company B which aligns with my career goals and job responsibility.