New MacBook says "USB accessories disabled" for iPhone 7

Just bought a new MacBook Pro with two USB-C ports. Of course it needs an adaptor for everything else to be conncected to Mac. Bought that. Now trying to charge and connect an iPhone7 and surprise surprise, it shows "USB Accessories Disabled", because of course Iphone7 doesn't have a USB-C charging cable. Here it goes again - everything that supposed to be simpler is made more complicated again... it's been that you could not connect Apple devices with other brands, now you can't connect Apple devices in between themselves! How do I connect an iPhone to Mac without buying something again?