BAD CUSTOMER SERVICE

I went to the store on 22/12/2018 and purchased a anniversary gift for my wife which was coming up in January 2019. I got her a gold chain and cross. I gave that on her on the day of the anniversary only to find out the chain was too short. I went back to the on the 10/01/2019 to return it but was told there is a 7 day return policy.it does not state anywhere on the till slip or in the store .I spoke to a manager (POOBASHNIE)on the 10th of January who agreed to do a refund only to go to the store to find out that she denies ever telling me that.