The legal battle between Apple and Qualcomm drags on. After Apple accused the chipmaker of ‘double-dipping‘ by charging once for a chip and again for a patent license, Qualcomm has hit back.

Qualcomm’s response to Apple’s latest filing says that Apple wouldn’t even have been able to make an iPhone without its patented technology, reports CNET.

At the heart of the dispute is that Qualcomm refuses to sell its modem chips to any manufacturer unless the company also pays a licence fee for its patents. The licence fee takes the form of a tiny percentage of the cost of the device, so as iPhones get more expensive, the licence fee increases.

Apple argues that, while it does rely on Qualcomm technology, it’s not fair that the chipmaker benefit from enhancements to iPhones in other areas.

The issue may be of particular importance at a time when it’s rumored that the iPhone 8 may be the first iPhone to break the thousand-dollar price point for some models.