No After-Sales Service

We have booked Thrifty's services through Rental Cars.com on a few occasions, and every time the after-sales service has been atrocious. They do not send the tax invoice once the service is complete, one has to chase them for it for days. When they do eventually send it, they have the incorrect amounts and details; and you once again have to chase them to amend the invoice. They do not respond to emails, eventually one has to call them and then they respond, but still with incorrect details. Eventually they just pass you on to some other company who didn't even feature in the booking process, providing absolutely no contact details, just, "sorry, call these people", and you end up on a goose chase of no end, still with no accurate invoice. How difficult can it be to supply an accurate invoice and why all the referrals to a company who wasn't ever mentioned when booking the service? We will certainly not be utilising their services for our company car hires again.