Bad service by MotorVaps

My mother's car was due for service in February but a consultant from MotorVaps advised that a 10 to 12 months time since the last service has not lapsed. She went to try and service her car today but was turned away again because the mileage was over 1500. How must she align exactly 10 month intervals to a specific mileage especially now that we had been faced with a pendemic and most service stations were closed? I am not happy with the service from MotorVaps and i want my mother to be compensated all her premiums back since July 2019 from this **** of a company.