How does SMS verification such as Mob, aggregate data send text messages to our phones?

I found some cases of sending SMS messages to verify SDK , such as Mob, aggregating data, etc.

how do they send text messages to phones we need to verify? Is it because of working with a company like Mobile Telecom?

Mar.07,2021

SMS cat check it out.

MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1b37b0c-2c0c9.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b37b0c-2c0c9.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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