Sonic telecoms

Anybody out there that has difficulty with sonic telecoms Internet services.. My wife and I been sending emails about no Internet connection but nothing was done to fix it and they took money every month from her account for service we didn't evan use so we went to the bank and cancel the debit order.. Now they threatening her to blacklist her.. How in the world can you pay for something you didn't use or get no communication on your emails you sending them.. I will neva make use of them ever again and I am getting legal advise regarding there threat