Dont trust Mrpmobile

I got a call from one of their agents 2016 that im receiving a free sim card with benefits etc. I never used the sim or put it into a phone because when I received the box I saw there where charges. I never used the sim or placed it in a phone. A few months ago I paid off my full balance and the next month I still had a balance I went into mrp and they told me its mrpmobile and they billed me every month since 2016/11. I sent them an email still waiting for a response. I just want to know how could you charge me on something you said is free and on what number did you bill me without activation of a sim?