Stop spam calls

I recieved two calls today, And two calls yesterday from this number. Both days I tried to call back, But I just get a dead line

This number called my sister about PPI which she has already done. The guy calling threatened her with taking money (£100) out of her bank account (of which she had not given any details) because she would not co-operate. How shocking is that. Just imagine if it was an elderly person who may have given their details without realising what a scam it is and my sister and I are in our 60's but more aware. Surely something should be done about these calls?

Wankers

Rings but never speaks