Vodafone — ISD call which I haven't made

I have been using this number for more than 16years but haven't faced any issue with bill amount.but to my surprise my December 2021 bill issued by the company has ISD calls of 23 different number. My pack is of 399+ GST which comes to 470 approx every month.but this month bill is of 2344 rupees.When asked about this to customer care executive they says it is genuine.and can only give discount of 250 rupees.now if have made those call then why discount..but i haven't called any such number.in fact in my whole lifetime with this number from hutch to voda I haven't called any ISD number. And in 1month how can I make 23 different calls. Please check those call with my IMEI number of my phone as I think any mischievous things is happening with my number. I want full waive expect my regular plan package cost.