Thank you for your query, I'm pleased you have considered Plusnet.
I have been unable to locate your account from your Community username, this may be because systems have not updated fully, especially if you have joined over the weekend, so I apologise for the general answer I give here.
With most orders, you are advised of your installation date within 48 hours of our suppliers Openreach confirming the installation dates for your order. This will be done via the Member Centre as well as your own email inbox, and by text message if you have chosen SMS as a contact preference.
Installation dates are subject to Openreach engineer availability in your area, typically this is at least 10 days from the date of your order. It is unlikely that you would have received a date before 2nd December if you have just placed your order, however I would suggest that you access your Member Centre regularly to see if there are any updates from us. You do not need to contact your existing provider about leaving, as we will handle that side of things for you.
I trust this is of help, however do let us know if you need anything further.
Thanks - LF.