BT 4000 Cordless Phone with Big Buttons & Call Blocking. The BT 4000 is a user-friendly home phone without an answering machine equipped with extra large buttons, bright clear display, and call blocking features. Developed for elderly users, the handset is also hearing aid compatible and boasts anAmplifybutton for a boost in volume.. Nuisance Call Blocking. The call blocking features of the BT 4000 empowers landline users to prevent unwanted disturbances from international and withheld numbers (which account for a large proportion of nuisance sales calls), which can be a useful function not only for the vulnerable elderly but for anyone who is pestered by repeated cold calls. It is also possible to bar up to 10 specific numbers from calling, and a Do Not Disturb mode can be switched on to silence the ringer for all but your most important contacts.. Easy to use. Designed for ease-of-use, the BT 4000 is straightforward to set up and use. The menus are clearly laid out, and the large