To say that we have employed a professional to do something for us.

Have/get + something + participle
Examples
I’m having/getting my hair cut today.
They just had their house repainted.
Note – get is very informal.

To say that we had to persuade someone to do something or that it is a favour.

get + someone + to + infinitive
Examples
I got my brother to do my homework or I was going to tell mum that he has started smoking.
She’s getting get friend to bake a cake for her wedding.