My daughter upgraded her iPhone 12 Pro Max back in Dec 2022. The promotion was $1000 for her phone which was in mint condition. Her iPhone 14 Pro Max was received in January including the return box and label to mail back her trade-in which she did right away. I have called customer service numerous times because we we were not seeing the monthly credit of $27.21. I have received many different answers - the last one being AT&T put in the wrong promotional code giving her a monthly credit of only $9.71. I would like to know how to resolve this matter.