Failure to sort out Vitality Drive and pay me monies owing

I paid for my annual Multipoint check of my car for Discovery Insure in June, but this was never reflected on my statement and hence I did not receive the correct cash back from Discovery. I phoned them 3 times and emailed them 3 times to sort this out and was told it would be addressed and I would receive back pay for the amounts they owed me. Now, 4 months later nothing has been done to update my vitality drive status or pay me the money owed me and I have just been on hold for 45 minutes to their call centre. This is appalling and unacceptable to treat customers this way