Someone asked me the other day, where can they get a new IP address? Their current IP address is "blacklisted" at Yahoo and Hotmail, I was told. It's easy enough to get a new domain name, but what about the IP address?
They let me know that their deliverability was suffering and that getting this fixed was very important to them.
I had to ask, though, why do they think the new IP address wouldn't have deliverability issues? Deliverability issues are reactive. Something has to have happened to make the ISP take a dim view of your mail, of your IP address. You don't just get blacklisted because your IP address contains a "7" in it. Something has to change in your sending or list hygiene practices. Are you engaging in email append? Are you buying lists? Are you sending to very old data?
Until you figure out what's causing the "blacklisting" and actually fix that, don't expect a new IP address to just magically fix everything. What will happen is, you'll try to warm that IP address up, it'll seem to go okay for perhaps a few weeks, but then you'll start to see the same issues on the new IP address that you saw on the old IP address.
It's kind of like changing your shirt because it's got blood on it. If you've got a bloody wound, changing your shirt doesn't actually close the wound.