Ola — Paid cash already OLA is asking to pay again

I booked a raid from OLA by default Postpaid payment has been selected . The driver was denying to take us without cash.. So we have to pay cash to the driver on the very same day i raised complaint to OLA. I said this to the OLA executive and they said we will look into it.. Everyday I'm getting twice or thrice calls from OLA and everyday I'm giving my concern that I paid cash to the driver. They are very rude. Today they are sending threatening message of taking legal action.
Please look into it.