Porting second phone line to FiOS

[Transceiver]

We have FiOS triple play with one phone line that was ported from a copper landline during the original installation.   Porting was very quick with hardly any disruption to service.  We have  a second copper landline phone number on a separate account that we want to port to FiOS.  When we called Verizon to ask about doing this we were told that the account for this line must first be cancelled and the phone number could be out of service for up to a month before it is re-established on the FiOS account.  We can't be without this number for that long, and a temporary number is not acceptable.  Porting itself is a simple process, so apparently the issue is the way Verizon handles billing.   Is it really the case that there is no way to port this number with minimal disruption?  We can accept a day or two, or maybe even three, but up to a month is impossible.