Internet slow

[Vicci3]

Since having a new router fitted, my Internet is very slow and all devices are struggling to get a connection.. I'm apparently on the max, it was never as slow as this and also an instant connection, however since needing a new router fitted because my mine just stopped, the Internet has never been as bad as it is

Can you help with this?

[Nettysmith]

Same with us - was upgraded to the best router, but since then we have lost all landline calls in the house, the WiFi to the tv is shocking and internet fluctuates so much making apps and my work computer slow as anything. 
can't seem to get anyone to listen at sky