Will not credit back my double charge

About 3 months ago I got double charged by you guys, I immediately phoned your branch and someone said they would get back to me about it but never did then I phoned again and someone said the same thing which they never did too then I emailed and got a automated response saying I would be attended too but again no reply. I eventually got through to someone about 2 months after the issue happened who confirmed I got charged twice and said I can have the money back or credit I chose credit as it was easiest and best but I was never credited so I phoned again got through to a lady in finance who said she doesnt deal with customer finance but would pass my number only the person who does but AGAIN NO RESPONSE it is now month 3 of being charged with nobody giving me my credit. Please either sort this out or take your stuff back because I will not support a business who seems to only care about themselves and not their customers