Yandex.Webmaster shows the warning “Your site might be related to SMS fraud” if the site allows money to be charged to users' mobile phone accounts without their knowledge. For example, the site might offer an SMS subscription to a service. However, information about the cost of the subscription isn't clearly visible or isn't provided at all.
For more information about SMS fraud, see the Help for Yandex.Browser.
Check whether this is happening on pages of your site. These methods are often used by various affilite programs. Make sure that the site only uses the code of affiliate programs if you are confident in their integrity. If you offer services for a fee, make sure that the terms of service are available and understandable for users.
If you have already fixed the violation, wait for an automatic recheck. If misleading content is no longer detected, the warning in Yandex.Browser will be removed automatically within a month. If the site still opens with the warning message after a month has passed, you probably haven't removed all the violations. In this case, check whether all the violations have been fixed, and wait for a recheck.
If you removed all the violations and waited for the amount of time listed above, but the message still hasn't disappeared, write to the Support service. We will try to respond as soon as possible.