Open up WhatsApp and along the top will be chats, status and calls.
Click on calls and it'll show a list of all calls made and received. The ones with a red arrow next to them are missed calls. Press and keep held down on the one you want to select to delete. A delete icon (a bin) will appear in top right hand corner. You can delete, or you can press and hold on another one, as you can delete more than 1 message at a time. The number of selected messages appears in top left hand corner. When you're ready to delete, just press the bin :)
If your phone isn't ringing when someone is calling you, it's probably due to the ringtone, as some ringtones are simply one beep.
go to the main menu and click on the 3 dots in top right hand corner. Click on settings, then notifications. Here you can change the ringtone for message notifications and call notifications - choose one that's quite loud and long ;)