Ola — Ola Postpaid Money Issue

On 25th January I took an outstation ride with Ola. Due to issue with Ola app i ended up paying in Cash. Now ola is chasing me to pay Postpaid amount which was deducted for the same ride. I have explained this to them a several times but they keep calling me for the same issue and threating me to pay them. What should i be doing in this case?

I aa getting 10- 20 calls each day and some times in an hour which i clearly think is harassment.