Reneging Summer Internship (Banks)

Hi all, was wondering if anyone has reneged on a summer internship contract (which you have already signed) and wouldn't mind sharing how it went?

I am thinking an email saying I wish to renege should suffice but would it be better to email them to request for a call and do it over a call instead? I know it's impossible but I'm trying to burn as little bridges as possible.

Context: both internships are with banks and in similar roles but the FT pay is about a 5k difference every month and I wish I could say I want to value my promise but my promise is not worth the 60k difference in compensation per year (assuming I get a conversion)