Anti-fraud sms regulation is aimed at preventing the scammers from abusing the system by making unlimited SMS requests to authorise into driver and customer apps.
The rule is as follows:
5 sms per account Id per day
or
5 sms per installation Id per day
or
5 sms per device Id per day
Basically, this means that a user can make no more than 5 SMS requests (attempts to get an OTP) from 1 device on 1 number per day.
After the 5th attempt the user gets the error "Verification request failed".
The number is blocked and allowed to submit next sms code request in 24 hours only.
Consult the post on Driver and customer "cool down" for details on the limit of cancellations for drivers and customers.