Avis - lack of response!

We were in an accident recently and Discovery covered us through Avis with a car rental. The agreement was for a month. collection date fell on a Sunday. Agreement on the day of receipt of the car was that the car will be collected on the 20th of September as scheduled, the 20th arrived, no collection. Monday morning the 21st I get to work and call Discovery advising them that collection wasn't made and I will not be liable for an extra day rental. I was assured that I will not be charged for an additional day. car was still not collected, so I call Avis directly and I am assured the car will be collected the next day....once again I mentioned I will not pay additional... which I was also reassured of no additional charges. when I asked why the car wasn't collected as scheduled I was told that they don't work on sundays...so even if I decided to turn in the car, was I supposed to turn it into a closed depot??? well surprise cos I was charged for an extra day, I have sent mails asking for this to be investigated and no response to date, hence my complaint to Hello Peter.... maybe now I got your attention Avis?????