Unauthorised debit from Uber.

I have been having a very bad experience lately with uber. Whenever I request a trip and pay by card it's either I end up being charged double the amount of my trip or there is an extra amount that get debited from my card later after my trip. I took this up with them and the only explanation I get is that the amount debited after my trip was a hold but they refuse to refund me that amount it has now been 5 days after that amount was debited and I haven't received my money back yet.