Car been in for repair

Customer comes into garage with his car on the back of a AA recovery truck. I spoke with the AA patrol who advised the cambelt had snapped. The boss was not in that day. On his return he asked me about the car and I advised him the AA patrol said the cam belt had failed, the boss replied, we won't be doing that job. Not my concern so I said nothing and walked away. The boss went away for a couple of days and after the car had been with us a week, the customer turned up asking about his car. He said, the car does not look as though its moved since last Thursday, and I replied, no its not. Did my boss not contact you to advise he was not going to do the job!! No the customer replied, so I then advised that my boss said he's not prepared to get involved with it. Customer was or seemed a little upset as nobody told him they car was not going to be repaired, which is understandable.

Out of the blue sort of speak, the customer asked if I'd repair his engine! I thought about it and my understanding that my boss said he did not want to do it meant to me anyway that if I wanted to do the job, then I was free to do it in my own time elsewhere, am I wrong on that!

So the boss returns from his vacation and the car is still at the garage. He asks me about the car and the customer and I said he came yesterday and was not happy that nobody rang him to tell him the job was not being done! I advised the boss that the customer had asked me to do it because you said you didn't want to do the job for him. The boss didn't like it but I said to the boss, I've done nothing wrong in my opinion because you said you didn't want the job, and I did not tell the customer I would do it, he asked me if I'd do it for him, I never said anything. 

Did I do the correct thing taking the job on?

The customer asked me before the car was touched how much the job would likely cost, a good estimate based on experience was given. initially the customer gave the view he didn't want to spend the money, but of his own free will then told me to do the job. So in May I recovered the car to my own private workshop and set about repairing the engine. The engine is fully repaired now and has been road tested and has no faults mechanical or electrical now. The customer was contacted and he said he would text me his details to email him my invoice so he could transfer funds to my account. The text never happend. I rang him about two weeks ago and spoke with him on the phone where he said he was going away till last Tuesday and on his return he would ring me to settle the invoice. No such phone call or text has occurred. We are now at the end of August from May. 

What should my best course of action be from this point forwards...