No help with changing OTP number

We app**** for fibre and everything was installed quickly but we have been struggling for 3weeks to get the service activated. The person who assisted us with the sign-up entered the incorrect cell number and to change it we've been shunted from pillar to post. we've completed 4 different documents to get the service activated and the OTP cell number changed but to no avail. I have never been so disappointed with a service provider as i am with them.