Thee first scenario. Mobile number registration using different Mobile Applications or Sites to earn on sms traffic, in some countries like Azerbaijan A2P sms price is more than 0,22 cents in other words SMS pumping fraud occurs when scammers exploit a phone number input section to obtain SMS-delivered items like one-time passcodes, app download links, or other content. These messages are distributed to a series of numbers overseen by a particular mobile network operator (MNO), and the perpetrators receive a portion of the resulting earnings.
The second scenario. mobile numbers also are used by spammers/scammers with a final goal: spam, create posts, likes, views, comments, scams, pump-and-dump and etc. In this scenario main goal is not the traffic money.
The third scenario is the most dangerous and the most difficult to identify. This is when there is a mass registration of new accounts from different phone ranges and then these OTPs are sold to a third party for use of these accounts by bots. Thus creating non-sustainable activity there.