So the secret here is to take control of the conversation from the start.
Behave like you were expecting them to ask these questions and you know how to answer them.
First thing you need to know is:
Never tell your current salary in the first call. You lose the leverage to ask for a higher salary.
If they ask for your current salary, tell them it's not important. What's your budget for the role?
Then when they ask for your expected salary:
The key here is to make this bracket as small as possible. Do some research online, ask your peers/seniors what's the market average these days and then give a number based on your experience.
The smaller and specific the bracket, they are gonna know you know your worth.
Hope this helps.