Can two different RDC promos on separate EIPs coexist on the same T-Mobile line in 2026?

I’m getting conflicting answers from T-Mobile Care and wanted to see if anyone has actually done this recently.

I currently have:
iPhone 16 Pro on an existing EIP with promo P988 / ID240725
About 4–5 payments remaining
Go5G Plus
Enough available financing

I want to purchase a Galaxy Z Flip8 on a second EIP on the same line and use a separately owned/paid-off Galaxy S20 5G as the trade-in.

The new Flip8 trade-in promo is R760 / ID260641 ($1,100 off).

T-Mobile Care confirmed that multiple EIPs can exist on the same line, but they’re telling me that activating R760 would cause my existing P988 promotional credits to expire because “only one promo can remain active on one line.”

I’m not trading in the iPhone 16 Pro and I’m not trying to replace/pay off its EIP. These would be two separate devices, two separate EIPs, and two different promo IDs.

Has anyone recently had two separate EIPs with two different RDC promos active simultaneously on the same line? Specifically looking for experiences from 2026/current T-Life system.

If you’re a T-Mobile employee, is the current rule actually one RDC per line, or one RDC per EIP?