Can OC and CA report same debt?

Of course they can. You didnt pay them.

If you pay the CA, nothing is changed on the OC's tradeline...it should already be reporting a zero balance. The status would still be charge off or sold accoiunt.

The collection agencies will report the debt that they own now. Even if you persuade the collection agency for a "pay for delete", the charge-off status will not be removed. Only the original creditor can probably remove it.

If you pay the debt with the CA, wouldn't the OC have the same information? So,....the amount would stay the same, with the OC, but, it would show 'paid' with the CA over the same debt? Is there anything that can be done about this?..I mean can WE have the debt removed under the OC?

Both an OC and a CA can report a balance at the same time.
Initially, the OC owns the debt. When they decide to place the debt for collection, they can do one of two things. They can assign collection authority to a debt collector, while retaining ownership of the debt, or they can sell the debt to a debt collector.
In situation one, the OC continues to report the amount of the delinquent debt under their ownership. When the debt collector reports their collection to the CRA, what they are reporting is the amount of the debt thay are authorized to conduct collection activities upon. Both are not actually reporting debt, The OC reports debt, and the debt collector reports balance of the debt they are attempting collection.

In situation two, things subtly change. Once the OC sells the debt to a debt collector, they no longer have debt owed to them, and must update their account balance owed to $0. At that time, with the transfer of ownership probably being unkown to you, the balance being reported by the debt collector becomes both the amount of the debt they are attempting to collect, and of the debt itself.

Ownership of debt is not something they are required to inform you of when transfer of ownership is made. The only real way to discern this from your CR is when the OC updates the debt balance to $0. That is a sign that the OC has sold the debt.