Many repairs go smoothly. Some do not, and the difference often sits in the paper. A shop writes an estimate, you approve it, the work begins, and the final invoice arrives longer than the estimate, with a labor line that grew, a part that changed description, or a charge for something nobody mentioned. When a service contract is involved, that drift can make it harder to tell what was approved and what was not, and it can turn a simple claim into an argument. Catch it at pickup, while you still have the leverage.
Know what drift looks like
Drift shows up as new lines, labor hours that do not match the estimate, a different part description, a diagnostic charge that was never discussed, or a repair described as maintenance on the bill when you understood it to be a repair. Each of these can be legitimate. Each one needs an approval you can point to.
Line up the estimate against the invoice
Put the approved estimate next to the final invoice and match every line. Mark anything that is new, changed, or unexplained. For each new line, ask who authorized it, when, and how they reached you. A shop may say a technician found something during the work. That may be true, but the question still stands: did you hear about it before the work was done, and did you say yes?
Stop the work before it grows
When the shop finds more, ask them to call you before they start the additional work, and ask them to describe the finding in writing or by message. Say what you will approve and what you will not. Ask whether the service contract requires the provider to authorize added repairs before work begins, and if it does, ask the shop to confirm that authorization before the extra work starts. Ask whether a part is a wear item or routine maintenance under the contract, because some contracts treat those differently from a failure.
Before you pay at pickup
Do not sign the final invoice until the lines match the approvals you have. If a line has no approval, ask for it to be removed, explained in writing, or taken to the provider before you pay for it. Ask for a copy of the completed invoice, the parts list, and any notes from the technician. Write down the time, the name of the person at the counter, and what you agreed. Keep the file with your contract.
If your contract's provider handles its own claims rather than passing them to an outside administrator, you may have a direct line to raise the issue with. This site has a list of providers that handle their own claims, so you can check which route your contract uses before you need it. See the direct vehicle service contract providers that handle their own claims page.