No feedback resulting in disconnection

I received a final demand from Vodacom on 27/02/2019 to say that I need to make payment within 21 days or send an email requesting a payment arrangement, I sent an email to them on the 04/03/2019 which generated a ref number stating that they need to contact me to make arrangements, when I call them now, they say its been handed over, however they didn't not respond to my email to make arrangements? Now I have lost the number because they did not call me back as per their email?