Help with my Cello strings!!!!?

Question

I just rented a cello and the strings are loose and out of tune. but when i went to tighten the pegs, they would like spring back. it wont tighten! I have no idea why though...

Answer 1

 Im having the same trouble with my cello and its new the guy at the store did it but then i had to travel with so i had to loose the strings and take the bridge off but when i try to put it back and tighten the strings with the pegs the pegs just unroll again. 

Please Help :D