Step 1. Enable auto-start
Open the Phone Master app → Auto-start (App auto-launch), or Settings → Apps → ProZvonki and find the auto-start item. Enable it for ProZvonki so the app starts in the background and after a reboot.
HiOS · XOS
Tecno, Infinix and itel phones (made by Transsion) run on the HiOS and XOS skins with aggressive "freezing" of background apps to save power. Because of it, call notifications disappear and reminders don't fire. Below is how to enable auto-start and take ProZvonki out of freezing. Item names differ slightly between HiOS and XOS, but the meaning is the same.
Open the Phone Master app → Auto-start (App auto-launch), or Settings → Apps → ProZvonki and find the auto-start item. Enable it for ProZvonki so the app starts in the background and after a reboot.
In Phone Master find the power-saving feature — App freezer, Power Marathon or Ultra power saving. Remove ProZvonki from the frozen/limited apps list, or add it to the "whitelist" / "Protected" apps.
Open Settings → Apps → ProZvonki → Battery and choose Unrestricted. This stops the system from evicting the app while the screen is off.
Open the Recents menu, long-press the ProZvonki card and choose Lock (the lock icon). A locked card won't be closed by clearing memory.
Open Settings → Apps → Special app access → Alarms & reminders and enable ProZvonki (Android 12+). Make sure the app's notifications are on.
Tip: most power-saving settings on Tecno, Infinix and itel live in the Phone Master app — start your search for these items there.
FAQ
The power-saving feature is freezing it (step 2). Exclude ProZvonki from "Freezer"/"Power Marathon" in Phone Master and lock its card in Recents (step 4).
The Phone Master app has an "Auto-start" item. Auto-start may also be under Settings → Apps → ProZvonki. Enable it in either place.
Yes. itel is also a Transsion brand and uses the same power-saving and auto-start logic as Tecno and Infinix. All steps apply.