Please release my fibre line

Due to very bad service I decided to cancel my Supersonic fibre line and gave them one months notice, On 26 March 21 my line ceased working and on 29 March, I received a email from them stating that I owed them a clawback fee and as soon as I paid it they would release the line. I paid the full amount that was outstanding on the same day. After phoning the company at least once every single day they are still stalling the release of my line and this is blocking me from appointing another server, they have been paid in full. Surely this is an ******* practice?