"just found out they want to piggie back off the cisco phone system we have at out other location in cleveland. we are going to use SIP via the cisco system. now the question is how can we keep are local numbers? is that even possible?"
So, what is it like to be given the responsibility to make this happen, but you "just found out"? To answer the question - with a gateway at your site, you could keep existing numbers. Much depends on how they're delivered. Clearly, you're not well versed in this arena and, once you change over, there is a very good chance that things won't work correctly. Assistance beyond an internet tech forum would really be appropriate at this juncture. Unless telephones aren't important to the operation of your business. Best of luck!