Mahanagar Telephone Nigam [MTNL] — Bill payment

Address:

k-2/001, happy home commplex, shanti park, mira road east

I tried to pay my mtnl bill online, CA no. [protected] the first time it showed transaction failed and when i tried again, it showed successful. yet i received two deduction messages... the bank shows both transaction successful.

now, mtnl has a notice that says, " MTNL Delhi/Mumbai accept only full-payments; therefore you have to pay the entire bill amount. Also as MTNL accepts payments only against the current bill, you can not pay more than the bill amount. In case of excess payments, MTNL will reject the payment and will not adjust against future bills. Similarly MTNL will not accept part payments."

I tried to call mtnl customer care, helpline and online number, none of which i received any help from them.

how many days does it take for mtnl to reject and refund the extra amount paid?
i want the INR 885/- refunded back to my hdfc account
please help