Android Question android permission send_sms

i have write a program that have 2 text boxes and one button
At the first text box I write a message
and at the second text box I write a pnone number
When i press the button the programm send as sms the message of the first text box at the phone number from second text box.

The program works fine at my previouse telephones samsung siii neo (android 4.4.2) and HTC

Now I have a new telephone Xiaomi redmi 5a with android 7.1.2

When I press the button to send the sms it shows me a report that I dont have permission to send_sms

please advice
Kalarakis