@Nishant porting COCP nowadays is not that difficult, I have shifted all my COCP to Airtel. Its just that they require all documents which need to given and couple letter heads formats which they give. Its difference case if the number is give by your employee and they don't want to port.
I'll be writing soon my detailed process and all tips and tricks to get cheaper COCP plans on Airtel.
Reason: I ported due to lack of corporate support (once they wrote in email reply that this Vi COCP account does not exist, despite the bill getting generated with wrong GST number), poor network quality, Airtel COCP gave me more benefit for cheaper price then what I used to get for Vi.
Note: Airtel is now more interested in COCP customer since 2018. When we bought our COCP only two companies where given COCP that were Idea cellular & Vodafone India back then in 2007.
Back then Airtel din't have any COCP, even 2012 I once enquired but they were least interested to help me. But recently I ported all Vi COCP to Airtel COCP and trust me they keeping eye especially on Vi customers since Vi have largest COCP base.