Help calculating leaving contract early fees

[#1]

Hi, My contract goes until 20/8/20 and I'm trying to figure out how much would I need to pay to leave my contract early. I came across a document in the help that explains the calculation, but it was impossible to follow!

I have Unlimited Fibre + Landline (although the 1 year upfront payment on this ended already so paying monthly for landline).

Can anybody from Customer Services help? I tried calling, but it's not possible to get through...Thanks in advance for your help.

[#2]

Plusnet, 

No customer service on the phone and no customer service online. How are we supposed to contact you?

Could anybody please let me know how to contact customer service in any other way? You don't seem to have an e-mail either...
I understand it's a difficult time, but you still need to leave a communication channel opened.