On one hand I think it's ok for rental prices to go up as device prices increase. But that should never happen after a customer has a device, at that point the device price was already locked in. If they rent an additional device? Sure that one could cost more, but not the existing ones
Honestly I would love to see laws that make rental units without the option to purchase illegal. (With appropriate limits on how much the purchase option costs)
It could also be that they were dependent on subsidised oil imports from Venezuela but over the last year Venezuela has drastically reduced how much oil it's sending.