virgin active and MBD ****

i opened a gym membership at virgin active arcadia in 2016 and decided to cancel it in 2018 because i couldnt use their services anymore..they told me i have to pay cancellation fee which is fine with me so i started dealing with MBD and i told them that i would like them to do debit orders for 3 months so that i can pay eveything off and the first month i was able to pay it since i was a student working part time then i couldnt pay it anymore so i arranged with them to start deducting againg in december 2018 but they did not and i get harassing calls from MBD everyday. over 3 consultants have called be already this year and we did a re-arrangement again since i started working permanently but every month from this this they dont deduct the amount which frustrates me and i asked them to send me their banking details so that i can pay it myself since they dont honour the debit orders that we agreed on..MBD and virgin active is a money making scheme beause if they dont deduct like we agreed upon that means the interest rates are increasing on my side and even when they call to arrange it charges me. please help me out i just want to pay this and get over and done with it i dont even have MBD contsct numbers so that i can ask them why are they not deducting the money evey month like we agreed.