Jonathan’s iphone

Contact Apple support.. if software related they will help u if hardware u can get Apple-certified repairs and service at one of Apple Authorized Service Providers. The technicians at all these locations receive Apple training. They deliver the same high-quality service with genuine Apple parts. The repairs are backed by Apple. U can make an appointment here.

https://getsupport.apple.com/GetproductgroupList.action?locale=en_IN&caller=sfaqiphonerepair&SG=SG003

If it is still covered by Apple warranty, make an appointment at an Apple Store or Authorized Service Provider among this list: Apple – Location Selector

If it is covered by a different warranty / insurance, contact your insurance company and ask them what's the right procedure you need to perform.

Regards

Giulio

Take it in to an Apple Store, or mail it in to Apple.

See here: iPhone Repair - Official Apple Support