MCent — phone no. cannot be added

Sir, i use mcent for 5 days and when i have deleted the app and add different phone no.[protected] (Airtel) ne and i cannot add my jio no.[protected] ne along with the airtel. It says the no. Has been use in different account but presently i'm not using it right now. I have tried it 4-5 time on date[protected]. Now i have no other means to do but to seek your help.
Plz look after this problem.
Thank you.