General error Telecom doesn't have a default value with function in model

The problem seems to be with the model because it is returning value in three cases:

Solution 1:

//return some default value if none of the if condition works:
public function getPhoneType() {

        $s = substr($this->mobile, 0, 5);
        if ($s == "63905") {
            return "Globe";
        }

        if ($s == "63907") {
            return "Smart";
        }

        if ($s == "63922") {
            return "Sun Cellular";
        }

        return "Some default value";
  }

Solution 2:

Handle this on controller side:

$phone_type = getPhoneType();
$contact->telecom = isset($phone_type) ? $phone_type : "default value" ;

Solution 3:

Presently you might be having your column like this:

Click on Change and then set some default value

Try one of the above solution!! It should work.