No new debit order mandate, I was promised a 40 percent discount 2 months ago still waiting , I was told my account is on a positive but my credit report says am a bad payer experiene say I show contact you first

I am very unhappy with you lies and services. When selling my car as an accident car, I was told I would get a 40 percent discount on the shortfall by many agent now they keep telling me to wait and it's been 2 months . Worst part is when I call the lady said my account is on credit that's why I haven't received a new debit mandate 2 lady's.now my credit report came with a missed payment experiene says I should contact you to remove ,now I'm getting anything payment request on whatsapp. Why wasn't the money paid add and why 2months later I'm still not getting the discount I was told about,most I want my credit report fixed. If it means we go through all the calls let's do i***** just a lot that you gives are not doing. The last time I complained the lady did listen to me ,she made her own stories