Airtel — Refusal to remove additional SIM from my primary mobile NO

Pl refer to my primary airtel postpaid mob no [protected] and secondary mob no [protected]
I am requestin Airtel customar care repeatedly for last one month but instead taking my request they r offering me new plans and have refused to remove my secondary number
I tried portability but I am not getting UPC no with the answer that there is a contract with service provider
I am having primary No for 15 years and sec no for last 2 years