Why am I being charged for iMessage through data by Smart Communications in the Philippines?

Smart Communications is again charging me for Apple messages sent through data (blue bubble).

Last year Smart Communications charged me for Apple messages sent using data. They reversed the charges when I showed them the official response from Apple - that they don't charge for messages sent through data. It is an issue with the provider. So I thought that was the end of that. But in February 2025 I am again getting international data message charges for Apple messages. I filed a dispute. Then a day later I got an "explanation" from Smart Communications dispute center. I am paraphrasing: "When data signal is weak, the app charges for messages. This includes for messaging apps like Signal, Viber, WhatsApp, Telegram, etc." I told them I have never been charged by any of these apps. When the data signal is weak, I usually can't receive the messages or send messages. But I've never been charged except for Apple messages. I told them the same issue happened last year; and Apple then said it was a provider issue.

[Re-Titled by Moderator]