I've hired a car from Avis via BA.com a few times recently - the price being better than Avis direct on these occasions.

Each time, I'm asked to pay extra as the amount that I prepaid on BA.com doesn't quite cover it. This time if it was £7 for a 3 day rental from Manchester train station. Last time it was £19 for a weeks rental in Scotland.

For the purpose of clarity, this is not for any extra insurances or other add ons. It appears Avis calculate the booking at one rate and BA.com at another. When I questioned it, the sales staff said they couldn't do anything as that's rate the system generates. Has anyone else had this situation?

As an aside, the car was returned when the office was shut, but it is sold as a 24hr drop off site. There was an additional £5 charge that was also payable for storing the car in a car park. There is no mention of this on the BA or Avis websites ( I did a dummy booking again and nothing said about it).

If I was going to query any of these points would it be to BA (where I made the booking through) or to Avis?