Price increase for loyal customers only

I have an uncapped 10mb/s fibre package with Vox Telecom. My package is supposed to be R799 per month. In January 2018 it was increased to R834.95. There website still advertises it as R799 and when phoning in there sales department also quotes it as R799, but there accounts department says there existing customers are subject to an increase. The sales consultant then suggested I cancel my package and repurchase it to maintain the price of R799, but there may be some down time. Why do I need to go through all this trouble just to maintain there advertised price each year and avoid an increase. There is no indication of these increased prices on there website, nor do there sales consultants know anything about it. So the longer you stay with Vox Telecom the more you end up paying in the long run unless you willing to constantly cancel and repurchase the same product to maintain there advertised price.