Since these apps require a data connection for use, simply use WhatsApp / iMessage as you normally would with your eSIM line active. Please make sure your primary SIM line is not active in order to avoid any possible roaming charges from your primary or local carrier. In addition, we do not recommend setting up a new WhatsApp profile using one of the phone numbers provided by us for use with our voice service, as these numbers are temporary numbers that will be released back into our phone number pool once your plan expires.