[Support] Receiving esm_class==4 for non-delivered SMS

[elhananjair]

Hello there, it's been a while since I started playing with node-smpp package, Thanks to this project, it helped me to get started with the package.

I have a code that sends SMS to multiple receivers, the clients get charged as they receive the SMS. The only way I am trying to calculate how many clients get charged is through delivery_reciept. But, one odd thing is I am getting the same esm_class value for SMS that didn't get delivered and delivered too.
Is this behavior normal or I am missing something? Thanks