How to file complaint about billing issue

I have never had a phone service that is so stressful, this is by far the worst company I have EVER went through, not to mention how 💩 the phone service is. We have 3 lines on our account and usually our payment is automatically taken out of my fiancés account but this time I paid it with my card so our lines would not get disconnected and so we wouldn't be charged $60 ($20 per line) for a reconnect fee. The payment submitted with a confirmation email being sent to my email, and they still disconnected our lines. This has happened at least 5 times in the past month and a half. Our phones at this point has been off more than on and we keep paying every time they say we owe. We called customer service and spoke to several agents as well as managers. One agent had me on hold and eas processing it to have our lines turned back on but we got disconnected and when I called back all they said they could do was apply a credit to my next payment which they tried making me pay before getting our lines turned back on. I did not pay this, because common since if ur willing to apply a credit then you r in the wrong.  But they sure wasn't willing to take off the $60 that got we got charged for our account getting disconnected even though we paid. As soon as we find another provider we will be switching. I have heard so many bad things about this phone service and should of listened but we put faith into this phone company and have not had a good  the whole time we have had our service. If you want to get screwed over then this is the company u want but I highly recommend you do not use their services. WORST EXPERIENCE I HAVE EVER WENT THEOUGH WITH A PHONE COMPANY!!!!!