Fuel complaint not resolved - suspected ****

Submitted a complaint re fuel but not resolved - usual delay tactics used. Three days into a two week rental in June 2019 I received a call to say car was "issued erroneously as it was due for a service. Please arrange to meet for a handover". I agreed under duress and filled the car pre handover, as usual. (Range indicator showed 709km) The replacement car however was not refueled although gauge showed almost full as I drove off. (Range indicator showed 492km). This is a suspected **** as the two vehicles were identical so the two range readings should have been approx the same. The service issue was probably contrived (can't imagine that Avis not would service their vehicles on time) and the vehicle changeover designed to provide staff with approx 250km free private travel pre changeover in each case. Avis persistent refusal to resolve confirms my suspicions.