Up to 8Mbps - that is the technology of the product, and they should have given you an estimate of likely speeds at sign up.
To know if the speed is sensible or not
and paste the text you get back for you number (hiding the phone number from us obviously)
2. Get the router stats from your ADSL modem, connection speed, attenuation and noise margin, and paste them and someone will reply with a judgement. http://www.kitz.co.uk/adsl/frogstats.php
3. Once you have the numbers from (2) try them at http://www.farina1.com/adsl
and this will give you an estimate of whether you appear to be running slow.
4. If you are running slower than expected, find the master socket in the house, remove the lower faceplate and connect to the test socket and repeat (2), hopefully better figures...not actual downloads will not improve at that point - but if better connection in a day or two things will improve.
5. If (4) shows better speeds look at the ring wire advice on http://www.thinkbroadband.com/faq/sections/radsl.htm...