Notification Profile:

1. How to configure alert notifications to be received via phone, SMS, and email?

You need to configure this while adding a contact or by editing a contact.

2. Why am I not receiving phone/sms notification?

This could be one of the following reasons

i) You haven't selected the notification channel for you in contacts tab.

ii) You haven't associated the escalation policy and the notification profile.

iii) While creating an escalation policy, you haven't selected the schedule which you are part of.

iv) You have disabled the notification profile.

3. How to reduce the noise and stay on top of high priority alerts?

You can define multiple criteria to filter alerts based on different fields such as display name, entity name, message, severity, etc. and get notified only for those events that matter to you.