Need a wired connection in different room than router

If you dont want to pay someone to run a new line you can buy an ethernet over power plug, most are capped at 45mbps but some of the more expensive ones will go over 100mbps. These plug into any 110 plug and have ethernet plugs . you will need 2 of these , one at the rg and one at the computer. they are safe, and vurtually no setup, just plug and play they will recognize each other. The downside is if the 2 plugs you want to be connected to are on different cuircuts they will not talk to each other. I have several in my home to various units (my particular type can run 6 plugs to the modem) Also another thing to remember is never use them for a uverse set top box they will pixelate and freeze like crazy. Also besure to plug them directly into the wall plug and avoid power strips

Is there any reason why you can't just run an ethernet cable from the router to the computer?  That's probably the easiest.  There are lots of places to buy cables.  It's easiest if you can run a finished cable (with the connectors on both ends) but you could also run a plain CAT5 or CAT6 cable, and there are various options for terminating it to a wall jack at each end and then using short cables from the wall jacks to the router and computer.  Replacing the router with a wireless router (or using wireless if the router has it) is also an option - there are inexpensive wireless cards or usb dongles easily available.

If you are asking about options for running a cable, you can do it yourself, you can likely pay AT&T to send a technician and do it, you can probably find a friend who can do it, and you can probably find a local contractor (either computer or electrician) who can do it.  That depends on what you are capable or and willing to do yourself, and what you are willing to pay for someone else to do it.

Please provide more details on what the problem is, in case this and the  other response don't really address what you are looking for.