Ha! Why didn't you post this two months ago! I learned this the hard way. I didn't even think about my credit card when we went on vacation. I called my cell phone provider though.
We were in Victoria, BC eating lunch and our card was denied. I had to sit out in the parking lot on my cell phone (ended up being a $10 call) to get it straightened out. They asked me how long I'd be on vacation and set it accordingly. The thing is we were using our joint account and I hardly EVER use that card at all.