The telephone is either busy or your ex is not picking up your call to speak with you.
Neither is your ex returning your calls in response to all the calls you've made to them.
But there are some guaranteed ways to make your ex return your calls.
Let your ex know that you are leaving town.
This is a sure way to guarantee that your ex returns your calls.
There would be some amount of uncertainty in this knowledge.
Many doubts will arise in your ex's mind.
Your ex will not know whether you are relocating for good with a new job or are you just going on a holiday or trip for a couple of days.
They will call back to find out more about the truth behind this information.
Give your ex an ultimatum.
Since your ex has not been answering your calls or returning them either, you could give your ex an ultimatum of never again getting in touch with them.
This will surely disturb them mentally.
Your ex will be convinced that you will not get in touch with them and the very fear of losing you forever will make them return your calls without delay.
They actually still love you and would not like to break off with you.
Show your ex that you are no longer interested in them.
If your ex suspects a possibility of your not being interested in them any more in the near future, then they will wake up to this fact and coming running back to you.
They will get in touch with you and make amends so that there isn't any possibility of your leaving them.
They love you far too much to accept the fact that you will no longer be interested in them.
They will return your calls as soon as possible.