Poor Billing Customer Relationship Management

I hired a car at Heathrow airport for 18 days, with all insurance protection included, and unlimited mileage, and against their quote paid upfront. Yet, when the bill arrives there are substantial "other" charges resulting in substantial additional cost. On returning the car, despite what budget says, there is no-one who reviews or explains the billing at time of return ... the key is taken, the car checked, and that's it. Next thing a bill arrives by email. So I wrote to budget for an explanation, and whilst you get a case number by e-mail, nothing happens, and they are happy in that the additional credit card charge stands. So really, Budget is not a valued customer (as they profess to be), but just a source of income at their discretion ... and any additional charges should be cleared upfront first, and NOT an unauthorized credit card charge. Having said that, the car was very good