If the contact's phone number is hidden in the Telegram Privacy Settings, then this contact cannot be written by phone number.
If the number is hidden, the contact can still be contacted by his @username.

You can write first in Telegram:

1. By @username of the client;
2. By ID of the client;
3. By phone number of the client.

When using a phone number, there are restrictions that depend on the Account Privacy Settings on the client's mobile device.

• If "Nobody" is set in the "Phone number" field in the privacy settings, then this contact cannot be contacted by phone number.

• If in the privacy settings in the "Phone number" field is set to "Everybody", then this contact can be contacted by phone number by writing to him first.

• If in the privacy settings in the "Phone number" field is set to "My contacts", then you can write to this client only if he adds your phone number to the phone book of his device.

When adding contacts to Telegram, you cannot add maximum 15 new contacts per day, so we recommend using synchronization of contacts with CRM.