Vox Sales not willing to help existing customers

Vox have advertised specials on their website (don't see anything stating it's only available to new customers). I've asked if I can take advantage of the cost saving and/or upgrade to a better speed package and was abruptly told its only for new customers and if I wanted the new package I would need to give a month notice, have the current package cancelled and re-apply for the special. Sales person was very unhelpful. Previously Vox assisted with a migration to a cheaper package and did all the necessary backend paperwork to facilitate the update. Vox want me to remain on a package which is R250 more expensive than what they offering new customers. Really not good customer service.