Airtel — airtel - number portability - worst customer experience

I have been using airtel number from last 12 years. From last two years there is no network coverage in my home and after multiple complaints there is no improvement seen. Finally wanted to shift to different service provider through number portability. Went to airtel outlet paid outstanding bill and sent msg to 1900. The reply got is upc cannot be generated as it is less than 90 days since it is activated which is absolutely ridiculous. Complained to 121 and at the outlet, they initially told there is technical problem but no resolution so far.in parallel, getting calls from airtel saying you have been using this number for so long why do you want to change but msgs says it is less than 90days old. After that they came up with logic saying bill plan changed 20 back which is also comes under condition of number portability. When i told i never requested, how airtel can change without informing customer they started saying there was discount earlier which is removed now hence i have to wait for 90 days. This way they are harassing the customer who has been with them for 12 years. Worst ever customer experience.