It looks to me like...
QuoteThe flat black cable coming into the box contains blue,blue&white wires and the orange,white wires. Is this the telephone service and DSL or just DSL?
The blue, blue/white wires are the line coming to the house from Verizon. This caries both your phone service and DSL. The orange,white pair are not being used.
QuoteThe two round beige cables coming out of the hole in the brick wall - one contains red/green/yellow wires
The red,green pair is the phone/dsl service going into the house. The green wire is connected to the blue/white wire, the red wire connected to the blue.
Quoteand the other is connected to a post in the center of the box
The ground wire to the house line.
QuoteTo disconnect the outside service while leaving DSL, I disconnect the red/green wires, right?
Wrong. You can't disconnect one without disconnecting both. Your phone and DSL run over the same wires.
I believe what MichiganTelephone is saying, and I agree with, is that if you want to isolate phones from DSL, you'll have to do it inside the house by connecting the red,green pair only to your DSL modem and not to any other phone lines in the house.
If you want to keep the phone service but connect it to an Obi, you'll need a DSL filter between the line coming in and the Obi.
Your wiring probably looks something like this...
[outside box]==red/green==[wall]==red/green==[inside junction box]==red/green==[phone(s)/DSL modem]
There's probably multiple red/green pairs coming from the inside junction box to the phone jacks throughout the house. Somewhere inside you have a DSL modem connected to the junction box (possibly to a phone jack). And somewhere in the inside wiring, you have DSL filter(s) before the line(s) reach the phone(s).
Again, as MichiganTelephone said, if you can get a picture of what's inside the house, it would help.
QuoteI could still cancel my Verizon land line phone service and keep dsl, right?
Yes you can cancel your Verizon phone service but keep the DSL (Verizon will most likely bump the rate on the DSL quite a bit).
QuoteI just couldn't test it beforehand.
You can test it by hooking up the Obi like it was a phone. Verizon line (with DSL filter) to the LINE port. Phone(s) to the PHONE port. Ethernet to your router. You may only be able to test it with a single phone without digging into the house wiring.
QuoteBut likely any phone calls made from the Obi would be competing with the dsl since they will be on the same line and probably have a lot of static?
I wouldn't say you're competing with DSL, you're using DSL for your phone calls. You're competing with any other device (computer) that is also using DSL.