"Before getting into a credit card dispute, wait until the unfamiliar charge actually posts to your account. Some pending charges will correct or disappear before they're posted to your account. Hotels and gas stations, for example, often place an initial charge on your credit card to request authorization for the transaction from your bank. Pending restaurant charges typically don't include the tip you added and may appear lower than you expect at first. "
I wish I'd known this 4 years ago. I was in Europe and gas stations from one chain used to bill me for more than twice what the gas tank would hold. I went to one of the two gas stations, called the gasoline company, and called my credit card company back in the US**, and in the end, wrote an apology letter to the manager of the gas station. I'm glad when I went to complain I hadn't yelled or said anything insulting to him. (I never do that.) While he was reading my letter, he put his arm around me and offered me a free coffee. And I took it. It's bad form not to accept what's offered like that.
**There were iirc two overcharges plus a more interesting episode where the pump would not accept my card. The guy there tried twice, and then I paid cash. But because of that, two charges showed up on the online bill. One of the two charges disappeared while I was talking to the credit card company on the phone***, the woman on the phone said. Pretty weird because it was several days after I had gotten the gas, and because she didn't know what was going on. The other charge disappeared a few days later. And I guess the overcharges turned into accurate charges.
I still don't understand why this has to happen. I can see when one starts to pump gas the gas pump putting a hold on one's credit card for the maximum amount any car can hold, or even any truck. But 5 minutes later, the pump knows how much gas was delivered, so why can't the actual charge replace the hold right then?
The hotel is different. When you check out and pay they haven't checked the room yet to see if you stole the television. And maybe restaurants are different because they put the credit card charge through before they present you the receipt and you add a tip? I usually tip in cash and I can't remember.
***BTW, if a USA 800 number won't work when you are out of the USA, calling with Skype will likely work. IMO it uses the internet to get to the USA, but then uses the phone system to dial the number, so at the destination, it looks like you're calling from the USA.