Thanks for taking your time to share this with all of us, my concern is how you managed to close the first deals if you knew nothing in that service. Didn't it require you to talk to clients in order to understand what their appliances issues were?
Hey mate, there is nothing to be worried about here. You just reverse engineer the process. There is no need to know the tech jargon because you won't be fixing appliances over the phone.
You ask the prospect about the kind of problems they experiencing and you tell them you are sending your technicians to investigate/diagnose.
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Example
Caller: Ring ring
You: Speed Tech, how may I help you?
Caller: My TV set is not showing picture I need someone to come over and look at it for me.
You: May I have your name, address and the time that you are available so that we can send one of our senior technicians to you.
Caller: My is Donald and the address is State House Washington and I am available at 10 am.
You: John, our senior technician will be coming to your place at 10 am today and assess your TV and give you a quote. If you approve the quote he will fix it on-site.
Is there anything I can assist you with?
Caller: That's all I wanted help with.
You: Thank you for calling Speed Tech.
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Not rocket science, huh?