You can customize your phone's ringtone with any music track of your choice.
To set up call ringtones on OPPO F3 Lite (A57), follow these steps:
Step 1: Navigate to 'Settings' and select 'Sound & Vibration.'

Select 'Sound & Vibration.'
Step 2: Choose 'Phone Ringtone.'

Choose 'Phone Ringtone.'
Step 3: Choose from the folder.

Choose from the folder.
Step 4: Select your favorite song as the ringtone.

Select your favorite song as the ringtone.
That completes your setup process. Best of luck.