How do I add an HTML code to my website so that when people click it, it opens a WhatsApp conversation with me?

What I am trying to do is add a clickable link to my website so that potential customers can click it (while on their phone) to open a conversation with me. So far what I have is:

```
<a href="intent://send/+316xxxxxxxxx#Intent;scheme=smsto;package=com.whatsapp;action=android.intent.action.SENDTO;end">Text</a>

```

Where `+316xxxxxx` is my phone number. However, this only appears to work for people that already have me as a contact and I am not sure it works for iOS. I've reached the limit of what I can do with my very limited HTML knowledge and I can't find any good info on Google, any help would be very much appreciated.