No stock of iPhone 6

I've been a customer for more than 6 years now of virgin mobile.From the start they had given with availability of handset,delivery time etc. I have been calling them each day for the last 2 weeks for an upgrade to the iPhone 6 but every consultant told me they are getting stock tomorrow and they'll phone me back...but its me doing the calling.Why do I have to struggle every 2nd year with an upgrade? Why don't they have stock like all the other network suppliers? Why don't they phone their customers back? My bill is close to a R1000 a month so in the past 6 years I paid them R72000 so surely they can arrange me an iPhone somewhere in South Africa,I think I need to close this contract.