Charged for car no longer on hire

Avis were informed to come and collect their hire car on a Thursday. They only collected the following Tuesday and charged me for this period. They claimed they were not informed about the car until then. The person that informed them confirmed they called the branch on Thursday but did not have telephone record.to prove. So I could not prove it. I refused to pay for the extra days but was handed over to a collection agency. So much for being a loyal customer and AVIS Wizard customer. They can now take their loyalty card and put it where the sun does not shine.