Need STAT Contractor ADVICE Please!!!

[Mandana Shahbazi]

We hired a company to replace our deck surface and railing. They quoted us a fair price. Under the deck, the worker added support joists. He told me, "If you call the company, they will charge you more for this. I added them to support your new deck. Whatever you want to give me for them is fine". Our original deck did not have these but I'm not sure if he is trying to manipulate our emotions and get a big tip or is it fair. It is not a complete deck replacement. Just the surface and railing. Should I compensate him, call the company or just tip him well. Everything else has been perfect. Thanks. Please answer ASAP.