I'm trying to buy a house and we didn't close on the 28th of june like it says so now we want to back out

Our house was supposed to be closed on the 28th of june, my loan officer says we need to sign the extension or there will be litigations...for what?.....If we were supposed to close on the 28th and it's past that date isn't the contract void? We weren't told anything about interest rate or payments they have just been plugging numbers haven't sent to the underwriters yet. Right now we are renting the propery with a month to month lease. If we signed the extension it will be for sep 30th, which means more months of high dollar rent. My fiancee need deferment letter from her college loans, about 10, she can't get those letter until september, but the loan officer wants her to apply for early deferment just for those 2 months so we can buy the house... but that program for deferment i'm pretty sure she can only use once...so what if we need it when the college loan are due....then we can't ask for deferment again. We do not want the property anymore. How can I back out?