Call waiting on esim not active while being on call on primary sim
Whenever I take calls on primary sim the second sim I.e E-sim is having no service. Can't use two sim together and doesn't have call waiting for secondary sim.
iPhone XS
This is how it supposed to work.
When you're on a call, an incoming call on your other phone number will go to voicemail, if you have voicemail set up with your carrier.* However, you won't get a missed-call notification from your secondary number. Call Waiting works for incoming calls on the same phone number. To avoid missing an important call, you can turn on call forwarding and forward all calls from one number to the other. Check with your carrier for availability and to find out if additional fees apply.
Using Dual SIM with an eSIM - Apple Support