Upgrading SIM800L

Good morning.

I have some SIM800L, some have firmware v13 and others V14
I can’t update them at V14, it tells me that the firmware does not match.
If I take one v14 and put the V14 on it, program it as SIM800C I upgrade it.
If I do it with one with the V13, it tells me it doesn’t match.
I found, a firmware v14 that you can put by setting SIM800L instead of SIM800C, but nothing changes, is the same thing, I think they have only changed a few bytes, to make the programmer accept it

How to upgrade it ?