Terracom Wireless Asked just to get my cell number changed but was told they need to charge me $18 even though they are funded by government Oklahoma City, Oklahoma

I received a phone from Terracom Wireless over a year ago in which I had ran into some issues with random numbers always calling the number they provided and harrasing me. Because of this I reached out to Terracom about the entire situation to see about possibly just getting my number changed, they asked me a number of questions and was happy to do so.

Fast forward to this year and I'm getting the same problem but it's not as if it occured only with a few days or even a week, this was going on for close to month that they random numbers would call with some even calling late around 10pm so I did what I only thought I could do in reach out to Terracom again to see what to do and perhaps I need to change my cell number again one last time, they proceeded to tell me they would need to charge me $18 in order to do so, now the problem is that the company is a funded by the govenment so I asked why am I being charged just change my number when there wasn't a problem before in which they did not give any real information other than telling me they need to do so in order the change the number.

I was under the impression that this was a company that is to provide those who are receiving governement assistance of some kind to be able to use a cell phone in which they are also being backed by the governement themselves?

There is something not right about the entire situation and am not sure if I am able to take any kind of legal action? Either way no one should be getting charged for a service that they clearly cannot afford who is again being governenet funded.