Wrong shoe size

In Feb 2015 I bought a pair of shoes which I only wore a month ago for the first and only time. The one shoe did not fit well and resulted in quite an uncomfortable wear. After which I put the shoes back into its box and never wore it again due to the pain from that one ware. Needless to say that 2 weeks ago I discovered while re-doing my closet that in-fact I was given 2 different size shoes. I called the store in question last week to discuss the matter and was informed by the ops manager that the matter can be easily resolved if I bring back the shoes with the payment proof, which I did the very next day. When I got to the store, only the assistant manager, Michael was on duty and I explained the query to him, at which point he printed the invoice from their system and advised that the ops manager has requested him to take pics and they would need to source that particular pair of shoes from a branch which still has it in stock. I left with the shoes and was told that I would be contacted with further feedback. On Friday, my birthday was completely ruined when I read a mail stating that there is nothing they can do to assist me as the shoes are not in a condition to be re-sold ?