Using placeholders should allow you avoid quoting and escaping. Your DB driver seems to be confused as to whether $row->{'cust_phsx'} is a number or a string. You might try something like this to make the data type explicit:

$phone_insert->execute(
    $row->{'cust_id'}, 
    $adtID, 
    $phoneNumberTypes->{'Day'},
    $row->{'cust_phac'}, 
    $row->{'cust_phpx'}, 
    $row->{'cust_phsx'} . "", 
    $row->{'cust_phex'}
);
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-Matt