Mere registration of a trademark does not automatically mean infringement. For example, if your trademark is for intent to use and you are not using your trademark to sell any goods or services, there is no infringement. Further, given that the other mark was for a different service, there may be no infringement. Moreover, if the applicant abandoned his mark, and his mark is no longer in use, there can be no infringement. Trademark rights are either obtained by registration, or by use (under common law). If neither registration nor use are in play, there is TM right that can be infringed. Also, if a trademark is not registered, the alleged infringer can plead the defense of "innocent infringer". In other words, someone accused of infringement of TM is not liable unless they have knowledge of someone else's trademark. Under the circumstances, you should not act in haste. Consult an attorney before you take any drastic steps, such as canceling your TM.
Disclaimer: This communication does not create attorney client relationship and should not be construed as legal advice.
It's very good that you're policing your trademark, but you don't need to worry about this old, abandoned, and different TM (although you should keep looking out for other potential infringers or claimants). TM cancellation procedures are only for TMs that have actually been registered, not for TMs that have been abandoned and never registered. Regardless of the impropriety of the cancellation procedure, if the abandoned mark was for services that are not likely to be confused with your goods or services, then this TM doesn't compete with your TM for the same consumers.
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.
Your question recognizes that trademark registration provides an exclusive right (sometimes referred to as a negative right) to prevent others from using the registered trademark for similar goods/services, but registration itself does not guarantee that the registrant is free to use the mark. It is also important to understand the federal-common law distinction for trademark rights, as you do here. Even though the similar mark you found may have been abandoned before the Trademark Office, it may still be in use, giving its owner common law rights in the geographic region of use. However, if a mark is not actively used in commerce, its owner cannot assert rights in the mark. (Note that this can even apply if a mark is registered.) It is also important to consider priority of rights. Once federal registration is obtained, the registrant has exclusive rights nation-wide. Any subsequent users of the mark will need to yield if the registrant enters their areas. However, a prior user of the mark who did not obtain federal registration will be permitted to continue use in his geographic region and prevent the registrant from entering.
With that background, there is no reason to cancel a registration based on a suspicion that someone else may be using a similar mark absent some other driving factor. So long as the registered mark is legitimately being used in commerce, it is valid and should be maintained. One cannot incur liability for merely owning a registration; rather, liability for infringement would come from use of another's trademark (registered or unregistered) in commerce.
There are commercial services available for searching not only federal or state trademark registrations but also common law uses of marks. These can be useful tools for both policing your own trademark (i.e., identifying potential infringers) and determining the validity of a trademark. You should also know that while trademark owners do not have an affirmative duty to thoroughly search for infringers, if a trademark owner deos become aware of infringers, the owner may risk losing rights if he does not enforce the mark against those infringers (whether by lawsuit, negotiation, or license).