How to stop flashers from disturbing

How to stop flashers from disturbingtyle-span" style="background-color: #674ea7; color: #45818e; font-family: Verdana, sans-serif; font-size: x-large;">you can stop flashers from disturbing by the following step below:

pick your phone and dial this number **21*171*follow by your flasher's number# to activate

If you want to cancel dial ##21# to ccancel