Terrible communication and service

I sold my vehicle in February, I called in and requested to cancel this service as my vehicle was sold and was requested to send a mail with no explanation of the process and I should receive a confirmation mail stating my mail was received. Regardless I have proof that I mailed them that very morning stating my intention to cancel and it be immediate as my car was sold. I then get an sms today staging I'm in arrears for 3 months and to expect legal action. I called and was explained that I need to give a months notice, OK fair enough so how do we get to 3 months of arrears. This company and their service is a ******* and I'd rather pay that little extra at tracker in future and to get better services than this. I will take this up as I have proof of email sent.