need to switch

I am junior applying soon for intern
I have contacts in ibd who explicitly told me they could much more help me get a job in their ibd versus s&t. these are top firms.

the problem is I am leaning toward s&t, though unsure.

i will apply for intern in ibd, i am under qualified, the market sucks, so I desperately need their help.

IF i do decide to switch at the end of my internships, how hard would it be and what would be the process to get my top choice of s&t desks. I am thinking to network my ass off. but once I express interest in s&t will they not give me a ibd FT offer? could I switch my internship to s&t after the first few weeks?

worst case scenario is I express interest in s/t and get no offer at all. or I get to s&t but get a really shitty desk or stuck in sales (not bad but not for me). kind of nervous of that.

thanks