Recently, a customer of ours had a swollen battery in her iPhone that needed replaced but was feeling unsure whether this would solve performance issues she was having. I gave her my assurance that we would do the best job possible, and verify that the repair worked after it was done.
Fact is, we don’t charge money until after your device is repaired and your issue is solved.
Guess what? We replaced the battery and her iPhone was almost as good as new.