html - how can I copy the phone number from phone book to the website textbox

Question

My users can't copy the phone number from their phone book(mobile phone/clipboard) straight into the html textbox. They usually fix this issue by copying the number from phone book into their notepad, and copy from notepad to the website textbox. How can I solve this problem?

My Textbox

<textarea name="newMessage" rows="2" cols="20" autocomplete="off" maxlength="500" readonly onfocus="this.removeAttribute('readonly');" placeholder="Type message here" @bind="@newMessage"></textarea>