Can you back up an old back up from iCloud
I had to reset my phone and get a new SIM card, it backs up automatically but I can upload a back up from a week ago
iPhone 13 Pro Max, iOS 15
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but I can upload a back up from a week ago
If you are saying that you backed up the phone with the old SIM card, and you want to use a backup of the phone that was made at the time you were using the new SIM card.......
You will need to reset / erase the data on the iPhone and then set it up again using the backup that you made a week ago to restore the phone. You will lose any new data that has been added to the phone since the time of the backup.
All of this assumes that you still do have the iCloud backup that you made about a week ago.
If this is not what you want to do, please provide more details.