At the moment my internet disconnects every time I receive a phone call . . .
<snip>
. . . also a crackling noise over the telephone when making calls.
Ah, if only you had mentioned those important symptoms in your initial post.
Reading the above, it now seems as if you have a defective joint in your pair somewhere between you and the exchange. The first thing to check is via a quiet line test. Unplug the router, phone and filter. Unscrew the two screws on the front of the NTE5/A and remove the lower front half of the face plate. Now plug the phone directly into the test socket so exposed.Call
17070, select option
2 from the menu and listen. There should be absolutely no noise -- no crackles, no hum, no pops, plops or hisses. The only thing you should be able to say is that the circuit is electrically live. To be 100% sure, you should test with a different wired phone plugged into the test socket. (Perhaps you could borrow one from a neighbour?)
If you notice any noise, report a voice line fault to who ever you pay for your
telephone service. Do not, under any circumstances, make any mention of broadband as that will confuse the issue. In most cases, once the voice line fault is resolved the broadband problem is also cleared.