Billed for technical issue

I was experiencing poor WiFi speeds (125-250 mbps) standing next to the gateway. I have a 1 gbps plan. I was also experiencing drops, and extremely high ping rates (150+), even for WiFi. I tried restarting my gateway, devices (even though it was across multiple devices) and nothing resolved the issue. I contact Xfinity customer support for help. The support agent walked me through testing internet speeds, power cycling the gateway, connecting my laptop directly to the gateway, and other diagnostic steps. They tried some things from their end, like resetting the gateway. After doing everything they were telling me, they asked me to run another speed test. Unfortunately the results were still poor. The support agent told me in order to resolve the issue, they'd need to send a technician out to my home. Since then I have been seeing better results. 

I was charged $100 for the technician visit. This surprised me because the customer support agent never mentioned the potential for being charged for the visit. From my perspective I had an issue, a phone agent wasn't able to resolve it for me, and verified that I was in deed having an issue, and the agent decided I needed a service call to resolve it. 

I called support to ask about the charge. I was very kind and patient, asking for an explanation as to why I am being charged for what the phone agent deemed necessary to resolve my issue. The representative from the billing department basically repeated over and over that they "unfortunately" are unable to credit it back with no logical reasoning to why I was charged in the first place. I decided to speak with a supervisor who informed me that if a technician is sent out it costs $100. I have had an Xfinity technicians out at other addresses for technical issues, and was never once charged. I didn't expect to be charged for Xfinity resolving an issue I was experiencing with their equipment. No body could explain to me why Xfinity decided to charge a customer for a technical issue they were experiencing that a technical support representative decided they needed a technician for in order for it to be resolved. Just that it was a visit for configuring my internet. What does that even mean? I didn't need anything configured, I was told the visit was necessary to resolve my issue.

Why is this a thing? I could never imagine calling a service provider about an issue I have, having the support rep verify over the phone that I have an issue, that I need a technician visit to resolve the issue, and then unexpectedly getting charged for it. Blows my mind that this is an acceptable practice. 

Unfortunately this single experience has made me question why I am still with Xfinity. Especially with family and neighbors sharing how much they love Google Fiber (their service and support).

Can someone from Xfinity salvage this experience and show my why I am still a loyal customer please? I'm just being open and honest.