[smaccona]

I don’t believe you can depend on support:

“The Replace Short Message feature is optional for the ME and the SIM but if implemented it shall be performed as described here.

For MT short messages, on receipt of a short message from the SC, the MS shall check to see if the associated Protocol Identifier contains a Replace Short Message Type code.

If such a code is present, then the MS will check the associated SC address and originating address and replace any existing stored message having the same Protocol Identifier code, SC address and originating address with the new short message and other parameter values. If there is no message to be replaced, the MS shall store the message in the normal way.

If a Replace Short Message Type code is not present then the MS will store the message in the normal way.”[0]

[0] https://www.etsi.org/deliver/etsi_gts/03/0340/05.03.00_60/gs...