When you "have" something, that means you already possess it. When you "get" something, that means you don't have it yet, but you are going to soon. But you are using alternatives of the words. "Got" is passed tense. "My hair looked bad, so I got a hairdresser cut it." actially works. If you wanted to make it into future tense, you'd say, "My hair looks bad, so I'm going to get it cut." "We're getting a new house built right now." actually makes sense because both "getting" and "having" would imply something currently happening (in this particular sentence.) "I didn't pay to get someone to repair my hair." would work, but "have" does sound better. I hope this was more helpful than confusing... /)_=

In your examples, if you use "get" in place of "have", then you must add "to" before the following verb. Also, with "get", you need to tell us who does the work. You don't need this with "have". Here are your examples, in all three forms: "My hair looked bad, so I had a hairdresser cut it." "My hair looked bad, so I had it cut." (note the word order) "My hair looked bad, so I got a hairdresser to cut it." "We're having workers build a new house now." "We're having a new house built now." "We're getting workers to build a new house now." (In a couple of these examples, "now" seems redundant.) I don't know what you mean by "repair hair" either, but anyway... "I didn't pay to have someone repair my hair." "I didn't pay to have my hair repaired." "I didn't pay to get someone to repair my hair."