Feeling a bit silly not thinking of this last night, but I figured out how to do this.
This is what works for my testing of the calls in case anyone else is trying to do this:
_req = platform.get(f'/restapi/v1.0/account/{accountId}/phone-number/') #this will be called once to get numbers
_tt = json.loads(_req.text())
_extId = _tt['records'][0]['id']
_setParams = {
'label': 'test'
}
_put = platform.post(f'/restapi/v1.0/account/{accountId}/phone-number/{_extId}',setParams)
So instead of sending all of the "Get" as params, just sending the label specifically as a param fixes things. Thinking sending the phoneNumber as a parameter is kicking back with that error since you shouldn't be able to change the phone number, so it's not an option as a parameter to send through that call, and most likely same for other fields returned in the "Get".
