02 sensor/catalytic converter

I brought my car to a mechanic and shared that I did my research and believe I need o2 sensor put in. I also told him to put in new spark plugs. I never got any calls so I reached out and he said he cleaned my catalytic converter with sea foam as it was very polluted. After that the engine light came off. Next day he cleaned it again. I asked if I should pick up. I picked car up to be told he did 5 hours of service at 60/hour. I never did get my sensor or plugs and now my engine light came on again. I’m out $300.00 and not sure what to do? I did not get an invoice for work and I’m puzzled to why he decided to clean the converter, not get approval in advance and let me know cost associated with the work. So, now that his method did not work in alleviating the engine light issue I believe if he did what I asked initially the car would be in good working order. Please advise.