Stop order on line while registering, what does it mean

[#1]

Hi,
I moved in my new flat over the weekend and had ordered plusnet broadband Monday last week, after the previous occupier (the landlord now) left.
today I am getting a message saying that there is a STOP order with the current provider (due to complete on 6/9/2014) preventing an order to be placed. It then suggests I contact the current provider to have this removed or I will have to pay £49.99 for an engineer.
What does it mean? What's the best way for me to proceed, without having an extre fee obviously, knowing that the previous occupier has moved of the country (but should still be contactable). Why would I need to pay £49.99 if the line is stopped? There is a phone line at the property.
This is not about moving a subscription, I'm getting a new subscription at the new flat.
Thanks,
Toutanc!

[#2]

Hey Toutanc,
Thanks for getting in touch.
It sounds like our provisioning team have identified the line to be a MPF line. This basically means it requires an engineer to visit the exchange to move the line into the BT network. If you can send me a PM with your new username I'll take a look for you.
Thanks,
Dan