I dropped Frontier/Verizon DSL a month ago and switched to Earthlink. Speeds were vastly improved initially, but then Frontier/Verizon accidentally reactivated my account and speeds dropped to previous levels. My Frontier is now deactivated and Earthlink started again but speeds are still slow and my IP addresses are still registered to Frontier, even after I get a new IP (which I have done a few times over the past week) it is still registered to Verizon. Shouldn't these be Earthlink IPs?
Typically, when you use DSL, you are using the physical connection of you local telephone company regardless of who your ISP is. For example, you can get your DSL service through Earthlink, AOL or NetZero but they don't actually own the lines to your home so they work with your local telephone company to provide you their service. You pay Earthlink and they pay part of what they get from you to Frontier for using their line.
Your IP address could be from either carrier.