Missing Refund

I got a Michael Kors bag from my boyfriend for Christmas but the latch on the bag was damaged. I made contact with them and they were amazing at assisting me to send the bag back, they inspected it and notified us that a full refund will be processed, up to this point everything went well. HOWEVER, it has now been almost 2 months and we are yet to receive our refund, we have send countless emails back and forth to no avail. I have asked them for the proof of refund a billion times, and they repeatedly give me the same feedback, that we must call the bank, I have told them I cannot ask the bank for my money without a proof of payment, and yet they just keep saying, as per our previous mail, please contact your bank. Eventually my boyfriend got involved and took over the emails, where they then rep**** saying the proof of refund was emailed in previous correspondence. After 2 months we have still not received a email and the last email that was sent to them bounced back. I cannot believe that we must struggle like this with such a large well known brand. I am heavily disappointed