I have gone through this a few times and learned the right way I hope as I am doing it again.
1- Make sure you can see the SmartJack, this is where the Phone Company runs the line too and where they end the connection, your provider, may "rent" the line from them but they phone company will test to that point and you can see the status Don't put it too high as the lights are on the top of the box usually and they usually lock it.
2-Make sure the CSU/DSU is included in the pricing, otherwise breaking out the Data/Voice adds to the cost.
3-Make sure the signal type they use is compatible with your phone system, there are a few types and most newer ones have no problem, but if not anothe Card would be needed
4-you can optionally get a T-Link for testing on your side, about $150-$200 but you can then test on your side and eliminate the other equipment from the problem, allows for looping etc.
I recommend these things because testing a downed T always results in them thinking it is your fault. I spent months with a T and PRI that had a bad power supply in the phone companies sytem that when it rained got wet and bounced my signal repeatedly.
One thing to conside is the price of going to an outside vendor. When you are with th eActual provider your calls to tech support are direct, with an outside vendor you call them, they call the phone company after they come to your site (maybe) to verify the problem and then yourely on them to solve it. We pay quite a bit for the local company but I also call direct to the test center when my phone service causes problems
The extra money is well spent when my service is down for less than an hour rather than a day as it was with a reseller.
(we have 400 incoming numbers with 1500 calls a day for a service company)
Steve