<?php
add_filter('em_booking_output_placeholder','my_em_custom_booking_phone',100,3);
function my_em_custom_booking_phone($replace, $EM_Booking, $result){
    switch( $result ){
        case '#_BOOKINGPHONE':
            $phone = $EM_Booking->get_person()->phone;
			$replace = str_replace('+','',$phone);
            break;
    }
    return $replace;
}