Employer paid me old wage instead of new.

[Riknos]

I have been working for the same company for a while, and on December 15th I took a new job at the company that was paying the same basic salary as my old one, however, minus the 20% shift allowance.

I have received my pay this month and I am still being paid the shift allowance, despite working a full month not in a shift role. I have read the various CAB articles stating my employer is entitled to take it back from me, however - I have not signed a contract yet for my new role (keep chasing HR about it...) so technically I'm still on my old contract, am I still entitled to my old pay? Or will I still have to pay back?

Anyone know if this technicality makes a difference?

Thanks.