I'm afraid line conditions can change over time, hence so can speeds available. You can make sure you get the best you can by ensuring the router is in the master socket and everything else plugged into the line is filtered, which will minimise any interference. Anything beyond that would require a fault to be raised, however I'm afraid as the line is running within acceptable performance limits it wouldn't be accepted as things stand. What kind of stats does your router report? Specifically the sync speed, downstream attenuation and SNR?
IP addresses are issued by ourselves and have no bearing on the line itself, so that wouldn't have anything to do with it.
Regarding the charge, the request was submitted to the bank as soon as it was created on our systems - beyond that I'm afraid we don't have any control over when it's accepted and activated.