How to let phone calls from a specific number bypass 'Do Not Disturb'?
You should be able to set an exception rule to allow calls and texts from certain people (All/Contacts/Favorites).
Different manufacturers will have different set ups but you should be able to get to this setting by going

Settings > Sound &amp; notification > Do Not Disturb > Exceptions

You may need to turn on Do Not Disturb to alter these settings.