Charging double interest on one account , cant allocate previous payments, dont respond to emails but quick to handover

Since RCS has taken over edgars account, no communication was sent re the change of bank details or email to send proof of payments. I saved edgars as my beneficiary on bank app & pay monthly. All of a sudden, they only received payment in Mar 2021 but not other months, but i've used same details.2: they included a 24 months plan together with a 12 months plan on my statement which both have different interest charged, no one can explain that to me til today. I have emailed them & called more than 5 times but no resolution, instead my account has now been handed over. They asked me to email my bank statement, why, how did they get the Mar '21 payment but not prev months??I also asked then to deactivate the jet club as all jet stores dont know anything about it but they charging it on my account. They are so unprofessional on their calls , they dont respond to email but quick to handover, how do you hand over an account that's been paid monthly?