Could a current or ex-pest control technician please answer my question?

I had my home and yard treated for fire ants 2 months ago. They are gone now, however, another ant species has decided to move in. My pest control contract only covers fire ants. Before I knew they weren't fire ants, I called a technician to come out. There were no ants "active" so he said to call him once I catch a sample with scotch tape, and that If it's not a fire ant, treatment will cost $200, but that he'll do it for $100 since I used to work for the company. I called him back a few days later. He returned and saw many active non-fire ants. He said to treat will cost $150. I told him the price I thought I heard him say before, but he only looked confused and said he told me $150. I told him I didn't have $150 since I thought it would be $100, and that I'll have to maybe call him back out in 2wks if my husband and I decide we can put that in our budget. He said he'd go ahead & treat the area where they are active by "pretending" they are fire ants, and that if his company calls to tell them they were fire ants. I didn't tell him then, but I do not lie. I saw he was trying to help me though, so I told him ok. His company called me, while I was driving, to re-schedule the next appointment, and said the tech told them he "started" a job but had to leave because I told him I had to be somewhere. I told the caller to call me back tomorrow to talk about it. When I got home, I looked over my copy of the "sheet" I signed for him. I noticed he didn't put a price, but under "note" he wrote, "treatment stopped-cust had to go. Will call in to reset." I was so busy having 2 hungry toddlers pulling on me that I didn't even read it first! I just wanted him to go so I could deal with my cranky kids. What should I do now? When they call back, I could get him in trouble if i told them the truth. I was wrong for even letting him 'try" to help. But now what do I do. I refuse to pay the $150, since I never intended to in the first place. I never told him I would. I told him we'd think about it.