Worst of the Worst - Can't Cancel Contract

Since last year my mother tried to cancel her contract with Cellc. She emailed them, she called them, and she visited the branch numerous times and still nothing happened. She even sent a letter. Now she keeps on getting calls she is in arrears, and they are going to take her to court and ect. This is a disgrace. I urgently need answers to assist my mother

I have several Case Numbers but still this is not sorted out. Will never recommend them