How can I increase call history on iPhone X

The call history is limited to the most recent 100 calls. You can’t change that.

You can't! iPhones only show the last 100 calls. Having said that, when you reach 100 and then delete a few calls from the history list, the same number of older, previously hidden, calls then appears. So they are somewhere on an iPhone, but there's no way I know of to access them. There might be some 3rd party app that can do this.

An idea might be to log on to your providers website or call them, as carriers sometime provide a list of calls going back a long time. Maybe they could send you a list. Hope this helps you! Regards, Ian.

No problem, I frequently answer a post only to see someone else answered it at about the same time.

Sorry kb1591, our answers got "crossed" due to my slow typing! Ian.