If the minimum speed guarantee ( MSG ) has reduced at each renewal, you obviously have a choice , renew at the new MSG , leave the service for an alternative, or continue on an out of contract basis with the original MSG which offers eventually the option to leave penalty free , although if out of contract that’s available anyway , no one holds a gun to your head , if you have no viable alternative because no other network provider has tuned up in your area , that’s hardly Openreach’s fault.
The MSG on ‘lines’ that provide genuine data from being in service, is based on the actual performance as opposed to a mathematical guesstimate used when providing a prediction of speed for an address without a working service , so an unresolved fault that lowers speed will result in the MSG being lower because the speed observed is lower , fix the fault , actual speed improves, so does the MSG , but ( as pointed out ) there are some issues reducing speed that are not faults , for example , the more customers connected to a FTTC ‘cabinet’ , the higher the chance your ‘line’ is affected by crosstalk ( interference from the FTTC service on an adjacent pair ) unfortunately the resulting ‘noise’ can result in the sync speed being lowered for stability.
FTTC is rate adaptive , if it’s the only option, you live with its limitations until a better alternative becomes available, there is no vendetta, no cunning plan , no Machiavellian scheme, to deliberately reduce speeds , the capacity to the cabinet ( and its utilisation) have no bearing on individual line sync speeds , to believe so is ridiculous, and ( as pointed out ) has nothing to do with BT , a company you don’t even use .
