Asda. Thinking of taking to small

I’ve worked for Asda ( England) now for multiple years as a SL and have never had an issue with payroll till September… I got asked to move stores by area manager to help a store whom GM was massively struggling… I agreed as it’s only an extra few minutes up the road from me and honestly was ready for a new store. the transfer went completely fucked up and it took till December to sort out. (that’s a different story) however I’m still missing 6 shifts. These are 13 hour shifts keep in mind. So around £1000 missing. I’ve mentioned it to store manager/ my TM multiple times and even shown her the time sheet from my clock in times. and exceptions from where my old store put no pay. They even agreed that I’m own money… it isn’t hard to see

The issue is I just keep getting told we’ll look at it and sort it. 6 months ago this was and I must mention it twice a week and they are still yet to do any pay adjustment… I’m genuinely so pissed off I’m thinking of taking them to small claims.