This means that you have more than one phone, and you can get the calls to go from one phone to another. Or the diversion can be to an answer phone, so that the caller can leave a message
- I tried calling her three times but it's busy - It's a pity that she doesn't get diversion
But, no, I think "call diversion" is when the call goes to a different number, usually to voicemail; but I think "call waiting" means that you can switch to the other person and say "I'm a bit busy at the moment, but I'll call you back" and then carry on with the conversation that you were having