landline keeps dropping calls and crackling.broad band speed very slow and can't excess my account

Hi I've contacted talktalk several times about my issues I've been having foe a few wks and still they haven't be resolved . 1 dropping and crackling off my landline. People can't hear me when I call and calls just drop. 2 my super fast broadband has very weak signal and speed is very very slow. 3 I can't excess my talk talk accoint saying password and username wrong. I've also written letters of complaints to ur head office and awaiting responce