line being held hostage

after numerous outages and unreliable service, as per your terms and conditions, I've given 30 day notice and requested a cancellation from supersonic in March 2021 in order to switch to another ISP. Supersonic have terminated their internet service and issued me with a refund in May, but are holding on to the fibre line. Basically, they are neither providing the internet service nor allowing another ISP to provide it. I have sent numerous mails and spent hours on the phone trying to sort this issue out but nothing is being done. Spoke to a very tactful but full of excuses (Tyrese) as well as a rude consultant (Mpilo) with no clue on customer service or etiquette. I've been without internet for 5 months. no reference numbers get given when calling, you need to make use of the individuals name but that individual is never available. Please assist as I'm at my wits end and beyond frustrated with your terrible excuse for customer service and very close to lodging a complaint with ISPA or ICASA or whoever regulates you people.