Fake call telstra

I just received a call today from this numbers and said they would cancel my internet collection from Melbourne due to conflict in something and then hang up. They were from a tape recording. During these few days I received so many called from somebody with Indian accent said they were from Telstra and told me some one had hacked into my internet and want me to check it through locked in my computer. Of course, I won't do it and then they got angry. Then I received this call today.

They said they were testra & wanted to fix my problem with my internet I am not with Telstra