Wireless

I'm assuming you mean cordless. Cordless systems only need one jack for the base unit. If you just have a jack you want wired for an extra phone your best bet is to call a low voltage contractor. 

When we move the box downstairs nothing works 

That's not much information. Do you have digital service (where the phone plugs into a modem) or do you have a traditional landline? If you want the jack to work do as stated and contact a low voltage contractor.