WAITING 3 MONTHS FOR REFUND

I had a instance where they needed to collect the incorrect text book and refund me, this is from July. They confirmed that they refund had been done in August - however to this day I have not received the refund, I have done a number of follow up's, asked for a manager to call me as well as sent my statement proving that I have not received the funds and no one bothers. The service is shocking! I am a single parent and every penny counts and the fact is that they have their book back which I paid for and I have not got my money back.