There are several ways to check if a mobile number is busy without actually making a call:
Call Waiting Tone: If the person you're trying to call is on another call, you will hear a call waiting tone. This is an indication that the number is busy.
Text Message: You can send a text message to the number and wait for a response. If the number is busy, you may receive an automatic response or no response at all.
Online Services: There are various online services that can check the availability of a mobile number. These services can tell you if the number is active, disconnected or currently busy.
Call Forwarding: Some people have call forwarding enabled on their mobile phones. In this case, if the person you're trying to call is busy, the call may be forwarded to another number or voicemail. This can be an indication that the number is busy.
Check Social Media: If the person is active on social media, you can check their status or last seen on the app to see if they might be busy. However, this is not always accurate as they could be active on social media while being busy with something else