How do you give no stars?

TFG recently made a mistake on my statement/installment, i queried it they promised to rectify it, today i receive a sms threatening me to pay a huge installment by 1 MAY and that my credit record might be affected. What's so frustrating is they got my installment wrong for March, they calculated and advised a new installment for me to pay i did so without hesitation now i receive these type of SMS's from the collection department that also cant even properly assist a client...useless