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When I first moved to Vodafone I got a speed estimate of 50mbps - 63mbps with an OpenReach minimum of 39.8mbps.
During the first 12-15 months of the contract the speed fluctuated quite a lot between 49mbps & 60mbps. I was fine with that, but then the last few months it's quite consistently been around 42mbps.
Now my renewal is due I decided to look around to see if I could get more speed somehow. I checked on Vodafone again using the postcode, landline checker and it states I can now get between 52mbps & 73mbps with an OpenReach minimum of 47mbps!
Not sure how long that speed has been available for, but I'm definitely not getting that currently, which means either there's a fault on the line or OpenReach/Vodafone reserve the speed increase for new customers! If that's the case, that's a ridiculous way to treat existing customers. If the min guaranteed speed is improved by OpenReach during the length of a contract, that increase should be passed onto the customer, it would definitely ensure loyalty.
Anyway, I've renewed with the new guaranteed speed at £23/mo with the updated router and a 14 day cooling off period. I just wanted to let others know that this also might have happened to your speed too.