Should I cancel the appointment?

Don't cancel, these technicians have brand new modems in their vehicle, request them a new one and have the old modem replaced also have the old one reported as defective, you get brand new but that is if the service person would agree.

I think you need to cancel it

The very first thing you should do if your modem/router is unresponsive is to switch it off, wait up to a minute and then switch it on again. This allows it to drop the connection with the ISP, allow time for the ISP to recognise that the connection is closed and close its end and then forces the modem to ask the ISP for a new connection. In nearly every case, this will be found to solve the problem completely. In cases where it doesn't solve the problem (even after trying this solution several times, increasing the 'off' time to make sure that the ISP has closed its end of the communication), there is either a fault at the ISP's end (which you should be able to find out by phoning the support line) or there is a fault with your modem/router. If it was supplied by the ISP, they should be happy to send you a new one free of charge. If it was one you bought then, of course, it is your concern and you should replace the modem. It is very rare indeed that the fault is in the cables unless they have been damaged in some way (and you would usually be aware if they had been damaged by being pinched, trodden on or stretched or something), so replacing the cables is nearly always bad (and expensive) advice. If your modem is now working correctly, it's a no-brainer and only polite to cancel the technician's call and will free up his schedule to attend to problems which realy need his assistance!

I think you must not cancel the appointment. Let the technician come and check. You never know. There might be other problems

If you do not cancel will they charge you?

if i were you, i will just tell the repairman that i did the work successfully but still i need to be sure if what i did was right.

well obviously you don't want to be out any more money. so why would you not cancel?

For technical aspect, I think it is better to let them check it.

If it's working, I would cancel and save yourself a bill for the technician coming out.

It was good you know how to fix your modem!

It could happen again and I would suggest to have the technician come so he or she can explain what happened and hopefully fix it so it won't again or teach you how to fix it.

If you will be charged for the repair, and yet the modem works...why not, cancel the repair schedule

It's your judgment call my friend.