Vodafone India — irrelevant bill charged

Address:

New Delhi, Delhi, 110020

I had been using a postpaid number for more than 4 years now. I always paid my biils on time. I moved to mexico with my husband and was using the number here. But somehow there was no network available for my sim which was a nightmare as all my accounts were linked to it. I could not make any transactions as i would not receive the otp. After 6 months when i travelled to india i made it a point to visit noida specially to get my sim converted to prepaid. The sector 18 noida vodafone store asked me that i had an outstanding payment of 1000 rs. I paid the money and they gave me the new sim and also told me that your postpaid number will be deactivated now. It was not easy as i did not have any other india number but i beared with it for good.
Please note that i was flying back the next day early morning. I asked a reassurance to the vodafone executive and made my situation very clear and he assured me the same.
The whole day and night i was waiting for the sms to get my prepaid sim activated at the cost of not being able to contact my family as my postpaid sim was already deactivated. To my horror i realized that there was no sms yet from vodafone when i was boarding the flight. When i reached mexico i realized that i have a message from vodafone saying that your request could not be processed because of an outstanding amount of minus (-) 300 rs. Which means vodafone took 1000rs instead of rs 700. Now they are harassing me to pay an outstanding amout pf approx. 8000 rs which they say was i used internet in international roaming. I was connected to the airport wifi to get in touch with my family i never realized that they would activate my postpaid sim for some stupid reason of their fault.

Kindly help me. I am really stressed out because of the vodafone harassment.