I had a bizaree conversation with BT Support today. I called BT sales to upgrade from Infinity 1 to Infinity 2 but was told I was already on Infinity 2. When I said that I was only getting Infinity 1 speeds i.e. 39Mb I was told that I should be getting between 43 and 60Mb (although the BT sales site says Infinity 2 is up to 76Mb) and the lady said she would transfer me to support to get this issue addressed. Support went through the usual rigmarole of telling me that they don't guarantee speeds but when I said that I might as well degrade to Infiinty 1 and save myself a lot of money each month since the speed I am getting is within the Infinity 1 range, I was told that if I did this the speed would drop down to around 30Mb!!! In other words, BT are being very deceitful in their advertising where they say that Infinity 1 speeds are up to 40Mb since they are now telling me that if I go onto Infinity 1 I will never get a speed above 30Mb. For clarification, the 39Mb I currently get is on a hard wired connection. If I go to a wireless connection I can get 39Mb if I am sitting next to the router but if I move 10 feet away it drops to around 5Mb!!!! I can understand to an extent that BT cannot guarantee a specific speed since there are a number of variables but this is first time I have been told that there is no way I could get the advertised speed on Infinity 1. How can BT get away with such misleading marketing information.
Just because you are on Infinity 2 does not mean you will get the max speed that it is marketed at. You will only be able to get the max speed that your line will be able to support. That is determined by such things as the quality of your line and the distance you are from the cabinet.
If you were to downgrade to Infinity 1 your speed would probably be 38Mbps which is the max capped speed for Infinity 1. This is because you are presently getting above that speed.
To determine if there is a fault on your line and what speeds you should presently be getting can you run this checker and post back a screen shot of the results
and use this speed tester then carry out the further diagnostics and post back a screen shot of all the results including your IP profile for up and down. This test must be done with a wired connection.
If you have a Homehub 5 can you also post the stats from 1-12 by logging onto the homehub management pages then troubleshooting > helpdesk. http://bthomehub.home/
The information you have been given regarding the speed drop on the phone is incorrect. If the maximum speed you can get on Infinity 2 is 39Mb it would be the same on Infinity 1.
Id also recommend you check out this link for help with wireless coverage