Someone is using my trademark.

Does that mean you haven't registered the trademark either? Does that mean that this company isn't using the word either? Then they're not using your trademark, and you have a business name, but you may not be using the word as a trademark and you haven't secured your own trademark rights.

You should try to register the trademark without further delay because your "common law" rights derived from your use, if you're actually using that word as a mark, won't fare well against users who have similar names/marks and have bothered to register them.

Will your local phone company re-assign a number from one customer to you just because that number happens to spell out your business name and maybe your common law trademark? I think that's extremely unlikely. Whether or not you get this phone number from the phone company or by buying it or renting it from the current user, you should still register your name/mark.

See an IP lawyer to help you figure out your intellectual property issues.

Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.

To add to the post above, I think you need to untangle in your mind what a registered trademark is versus an actual phone number. While many companies have phone numbers that they use as their brand name (e.g., 1-800-mattress), the brand name usually follows the acquisition and use of the phone number. Secondly, in many instances, even though the brand name is a phone number derivation (e.g. 1-800-mattress), the actual phone number used is very different from the brand name. That being said, having a registered trademark can be and is often part of a very powerful strategy that can enhance the value of and protection for your business. However, it is very unlikely that a phone company would force someone to relinquish a phone number, because it is a utility that is not really concerned with protecting brand recognition.

I hope that helps.

Disclaimer: This answer is for informational purposes only and does not constitute general or specific legal advice, nor create an attorney client relationship.