Airtel — double recharge problem

I had done the recharge of 399 on my airtel number [protected] and after that by mistake i had done the recharge again of 99. But they are giving me only the benefit of my 399 recharge. But the pack of 99 must be started after the ending of the pack of 399. This thing is happened with me with other operator also (Jio) but they first finish the one plan than start the another. Please sir take the strict action against airtel. They are just fooling the customer for there benefit.
Sir i had tried to solve the issue by calling them but refuse to do anything to help me