said by DuPie :How long ago was the modem purchased? 3web was purchased by Distributel a few years ago now.
A 3+ year old DSL or Cablemodem won't work very well on new networks (Docsis3 or adsl2) and won't support the newer speeds as ISPs upgrade networks.
If you bought one less than a year ago well that's a different story.
Any more details?
ADSL2+ is an old standard (and on its way out), ADSL2+ modems have bee around for a decade now, so no, a modem bought 3 years ago for ADSL will still work (as long as it was ADSL2+). VDSL packages are where you'd require a new modem purchase, if and when they allow BYOD for VDSL.
With cable modems, it depends if he's on a tier that requires channel bonding or not. If it does, it's recommended they buy a D3 modem even if he can get the same speeds at D2, D3 makes things simpler.