Vonage charges customer of 6 years $80 to disconnect because equipment was replaced to fix a problem. Internet

I have been a Vonage customer for over 4 years. Due to requirements to have a land line rather than VOIP for a job I am working, I requested to cancel service. I was told that there would be a charge of 80 something dollars to cancel because I received new equipment in May.

The reason I received new equipment is because my old equipment was not working and replacing equipment was the only solution they had to fix it. If I had known they would charge me $80 when disconnecting I would have just disconnected at that time.

As the customer, I do not understand why I have to suffer for the companies inability to fix a problem without replacing the equipment.

I talked to one Account Manager that told me I could return the equipment and they would credit back the charge. However, she said they would have to charge my account at the time I was talking to her to discontinue service. I discussed mailing the device before cancelling to expedite the credit and she said to just call back when I was ready to do that since I was in my car at the time. 

I called back after returning home and the person I spoke to told me I could return the equipment but that they would not credit my account for the $80. This is a complete Rip OFF.