what is the protocol for canceling with the dog sitter and Rover?

Not all of us are going to be able to do our trip due to our more reliable vehicle being totaled in a a very recent accident and we're not sure our older, more mileage vehicle will be able to make the trip. So my husband will be staying at home, and the need for a dog sitter is no longer there. We were scheduled with Heather for Dec. 28 and Dec. 29 (3 regular visits and 1 dog walking visit). I've already given my credit card information as of last Friday, Dec. 21.