I have just had broadband installed and I find when I use my phone there is a shhhh noise in the background.

I have 6 jackpoints in the house but am only using 3 or 4.

I've tried disconnecting the filters and devices and moving them around, I don't think any of them are faulty.  I find if I only have 2 phones connected there is no noise, doesn't matter which ones, 3 a little noise, 4 is intolerable.

I've tried doubling filters on each phone line, I'm not sure if it's helped.

The slingshot helpline suggested I disconnect the jackpoints I'm not using however when I did this other jackpoints that i want to use disconnected as well, so i guess my jackpoints are wired in a daisy chain.

Any suggestions on what else I should try?

Thanks.

Bruce