Complaining is impossible, either via the web or by phone, the ops are also requesting full password

Impossible to complain. I have called 4 times and two of those times ops have requested full password rather than charachters from the word. I am receiving frequent emails asking me to book an engineer as they say my broadband isn't working as it should, it's fine actually. I also need a postal address to return a landline phone as the label they sent is yodel but I am disabled and cannot reach the yodel store. I need a postal address to return the equipment?  Thanks