Double-charged, no payment or feedback

I made a purchase on the 24/12/2014 and it was charged twice on my debit card. The cashier told me that if this happens the transaction is usually reversed overnight and took my details down to contact me should this not happen overnight.<br> The reversal didn't take place and nobody contacted me. I returned to the store two weeks later & was asked to provide proof, I gave them my bank statement & was told that I'd have my money back in 7days, once again Lizz (Credit Manager) took my details & promised to give me feedback - sure enough, it didn't happen. I've called the store 3 more times & received different excuses, the last call being on the 28/01/2015 to Lizz who said the my money would paid on the same day & asked for my details yet again which indicated that the were not working on my query. I still don't have my money back, & no feedback has come my way. I would've really appreciated honest feedback & not be fooled. Your staff ought to realise the cost of this, the inconvenience my time & money (driving to the store twice & calling) - which can be avoided. The store has no right to hold on to my money without my permission, fix it urgently - otherwise pay it with interest.