A sales rep still should know by your records and if they don't they should know who to call. Now to try and answer your question. When you had AT&T service you had a t1 to the AT&T switch that switch requires certain line coding and framing format, depending on what you are using it for. Across the carrier it's always ESF it's converted on both ends (switch and to the local company) Bell South, if everything is done right is transparant so they don't care what the framing is they just pass on what they get, so they wouldn't know. Now things have changed, the local companys can now provide Services before they couldn't so now they need the information. Not knowing your CSU I can't be specific to it, but most CSU's have either an option switch or soft pad display where you can set the line code and framing, but there are a ton of different ones and I'm sure there are some that you buy that are hard set and can't be changed. Hope I haven't rambled too much and shed some light on it.
Bill
