GIF will not send through MMS if larger than ~500kb

Just switched over from Android. Have never had an issue sending GIFs via MMS, even when sending to other iPhone users.

New iPhone 15 Pro Max will not send larger GIFs. Smaller ones seem to send find but larger ones return an error. I have been in touch with the service provider (Optus, Australia) and they have confirmed there are no MMS file sizes imposed.

I have reset network settings, turned iMessage on and off, confirmed and toggled the MMS option in settings, my provider has reset the network settings from their end. There seems to be a limit for MMS sizes imposed from within the iPhone itself.

How can this be raised with Apple? Do they ever investigate things like this?

And before someone suggests I use an alternative app like Viber, I do not want to do this. I just want to send messages to a range of people via MMS and not be restricted on file sizes. What is the point of having GIFs available to send if half of them can't be sent or I have to buy iPhones for people I know.