When a number is ported (from Vodafone to Skinny) does Vodafone still have anything to do with call routing?

The reason I ask is that over the years I had a problem when with Vodafone in that callers would wait quite a while before I answered. They would often say that they nearly hung up because the phone just rang and rang but at my end the phone would only ring perhaps twice before I picked up.

This has occurred for a number of years across various phones at each end and with various callers. I am now aware that the same thing is happening with Skinny. So I just wondered if it could be some weird unresolved issue at Vodafone that is still happening because calls still route through Vodafone. Any thoughts?

Thanks.