welcome to the BT community forum where customers help customers and only BT employees are the forum mods
in order for the forum members to help please can you post the stats from your router (if hub enter 192.168.1.254 in your browser) and if HH5 then go to troubleshooting then helpdesk and if HH6/SH2 then advanced settings then technical log information .
Have you tried the quiet line test? - dial 17070 option 2 - should hear nothing - best done with a corded phone. if cordless phone you may hear a 'dull hum' which is normal
run btspeedtester with an ethernet connection not wireless and post results
Someone may then be able to offer help/assistance/suggestions to your problem
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