missing an offer- LSE/UCL

so i need AAA, but if I come out with AAB marginally, and my course isn't the most competitive at these unis unlike subjects like economics and maths, do you reckon there's still a chance? I know LSE is hella competitive but i Just wanna know if you're very close to an A but you got a b? since unis don't receive your raw mark, is it worth calling them up on results day and explain how close you were to the next grade?