Trying to access an account

I am currently trying to access my account. It has been in use since 2012 or so. I can't remember the password. I don't have access to the email that is on the account. The mobile number has been changed too.

I use an O2 mobile. I have recently moved and after much explaining, I got the address changed and asked for installation which required an engineer visit, as there is no cable box outside.  The call rep stated yes to an engineer then said it was self install. 

So disconnection on 16th Jan, install 17th Jan. Waited all the way to 5pm, no engineer but have received a self installation kit.  Not helpful.

My daughter's are helping me sort this as I am 81 year old with terrible memory and bad hearing.

Which would be the best way to sort my account so I can update the email, mobile number and sort installation?