telephone line disconnected

DreamMachine_2

I had an account with Post Office for my landline, trying to upgrade my internet with Zen internet i decided to let them transfer my telephone line at the same time, I was told this is a straight forward transfer, conseqently The Post Office have disconnected me before the transfer was complete, they now say that I will not get my original number back and left without a working telephone line how can Post office cut me off and not retreive my number when they accidently cut me off. my zen Internet is still working on the same line into the household so how do I get my old number reconnected ?
Thanks for any help