An elderly client is on fixed wireless with Vodafone (no idea why Vodafone did that when they can get 60 - 70mbps VDSL or Fibre). I should mention they are already a bit unhappy with Vodafone apparently due to multiple billing issues. 

Anyway, the fixed wireless is not performing well, to the point that TeamViewer is basically unusable. 

Pretty keen to recommend they change to 2D Fibre, but am unsure if I should recommend they try and do that in one step, or if they should change to Fibre with Vodafone first, then change ISPs. They do have a landline - if they were on naked, I wouldn't mind recommending the one step change, but I can see this getting messy. 

What would be the consensus here in this situation? Thanks!