Om Heating and Cooling

I had issues with my furnace where my furnace was not blowing hot air and the house was getting cold.
I called Hemant, the guy who owns this business and he mentioned he will come in 1 hour time and his service charge will be $90, which I agreed to.
The guy came and post inspection he mentioned that gas valve is not functioning properly and that need to be replaced. I agreed to that being changed.
When I asked for the cost, he mentioned that it will be $600. I was surprised with such high cost and so I asked for the split on how much is the product cost and what is he charging for the service (remember he agreed to $90 for service charge before he came). Initially he was reluctant to share the split but on asking multiple times, he mentioned that $400 is price for the the part and remaining $200 is for his labor (he changed this even though we agreed for the price of $90. The part change took him only 15 mins, not that his effort got increased here).
I highlighted to him that he is charging too high for the labor and we agreed on $90 but he kept mentioning this is what it is. Either get the work done or else give me $90 for the visit and I will leave things as it is. So basically in either scenario I was loosing money. I still agreed to pay him $150 for the labor.

Second interesting thing that happened, I asked the Gas valve details that he was replacing for which he mentioned that its market cost is $400. I checked the product details and got the price for the same product as $175 approx. on google. I was surprised and challenged that how can he tell me the price of the product almost 2.5 times and why was he telling me the such inflated price .
On being caught with this, he then changes his stand and was trying to cover up.
Considering the situation and he opened things, he was threating again and again that I will leave the work in between and you are still obligated to pay me $90 towards service charge.
I got the work done somehow as I had no other option. Once the work was done, I asked for the bill to ensure I have the proof of the work done and any issues I face tomorrow, I can prove it that this part was fixed by Hemant. He was very reluctant to give me the bill and was asking to pay him in cash. He inflated the product price 2.5 times and was making $550 for 15 mins work, still he was reluctant to give bill, one for evading taxes and second to do not leave a trace that he was heavily overcharging me.
I clearly told him that without bill I will not pay him money and only on that he went back to his van and brought the bill.

I am attaching the bill and product details for everyones reference.

Will not recommend to anyone because of dishonest service