Can it be this difficult to change a number for OTP's

<p>Your telephone system is cumbersome. It's a painful experience trying to change a cellphone number so that the OPT is delivered to the correct number. I've logged a query on your website but to no avail. I called Vitality to change my number. They did but still the OTP's are being deleivered to my old number. How many places need to be updated before my new cellphone number will change across all of your platforms. How difficult can this be?</p>