checkbox checked focus the conditional field

checkbox is for call-back – when checked the input field is shown to insert the phone-number. on Desktop everything works fine with f.e.:

$("input[name = 'rueckrufwunsch[]']").on("change", function() { 
   if (this.checked) {   
	setTimeout(function() { $('#rueckrufnummer').focus(); }, 300);
   }
});

rueckrufwunsch is the checkbox –
rueckrufnummer is the input field for phone-number

but it does not work on iphone/ipad etc.
is there a way to obtain that the input field is directly activated to input the numbers?

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