Taking out a contract at mtn is terrible there service is bad

I don't understand how mtn works with there contracts seriously my sister went into mtn and opened a new contract someone who doesn't have a credit history what so ever and got a phone immediately without waiting 2 to 24 hours i went into mtn to open me a contract for the first time and i had to wait 2 to 24 hours for me to hear that i got declined with no reason to knowing why i got declined what doesn't makes sense is to why my sister got a phone immediately and i had to wait so long your service is terrible i don't know how you guys operate seriously