Flutter add multiple value into map - flutter

Question

So I'm trying to create a flutter app. In my app user A can invite user B,C and so on to join the group, but the user invited can reject the ticket. The user ID that reject the ticket will be stored in the firestore to detect which id reject it and there's a reason why.
The database data looks like this:
- Rejected_detail_map
----Rejected_role_admin
-------- USER_ID_A : "REASON_TO_REJECT"
-------- USER_ID_C : "REASON_TO_REJECT"
----Rejected_role_member
-------- User_ID_B :"REASON_TO_REJECT_2"
I wanted to fetch the data from each rejected_detail_map in one of my page, and use that ID to get the information such as nickname, prof_pic, etc.
Here's how I do it:
if (data['reject_detail_map'] != null) {
if (data['reject_detail_map'].isNotEmpty) {
List rejectDetailKeyList = data['reject_detail_map'].keys.toList();
if (rejectDetailKeyList.contains('rejected_by_pic')) {
List picIdRejectList = data['reject_detail_map']['rejected_by_pic'].keys.toList();
Map picRejectData = {};
await Future.forEach(picIdRejectList, (picId) async {
try {
if (Provider.of<OtherUserDataProvider>(context, listen: false)
.getUserData(picId.toString()) ==
null) {
picRejectData[picId] = await UserDatabase.getUserShortData(userId: picId.toString(), context: context);
Provider.of<OtherUserDataProvider>(context, listen: false).setUserData(userInfo: picRejectData[picId], userId: picId.toString());
picRejectData[picId]['role'] = 'pic';
picRejectData[picId]['reject_text'] = data['reject_detail_map']['rejected_by_pic'][picId];
ticketData['user_reject_data'] = Map.of(picRejectData);
} else {
picRejectData[picId] = Map.of(Provider.of<OtherUserDataProvider>(context, listen: false).getUserData(picId.toString())!);
picRejectData[picId]['role'] = 'pic';
picRejectData[picId]['reject_text'] = data['reject_detail_map']['rejected_by_pic'][picId];
ticketData['user_reject_data'] = Map.of(picRejectData);
}
} catch (e) {
DevMode.log("Error: $e");
}
});
}
if (rejectDetailKeyList.contains('rejected_by_client')) {
List clientIdRejectList = data['reject_detail_map']['rejected_by_client'].keys.toList();
Map clientRejectData = {};
await Future.forEach(clientIdRejectList, (clientId) async {
try {
if (Provider.of<OtherUserDataProvider>(context, listen: false)
.getUserData(clientId.toString()) ==
null) {
clientRejectData[clientId] = await UserDatabase.getUserShortData(userId: clientId.toString(), context: context);
Provider.of<OtherUserDataProvider>(context, listen: false).setUserData(userInfo: clientRejectData[clientId], userId: clientId.toString());
clientRejectData[clientId]['role'] = 'client';
clientRejectData[clientId]['reject_text'] = data['reject_detail_map']['rejected_by_client'][clientId];
ticketData['user_reject_data'] = Map.of(clientRejectData);
} else {
clientRejectData[clientId] = Map.of(
Provider.of<OtherUserDataProvider>(context, listen: false)
.getUserData(clientId.toString())!);
clientRejectData[clientId]['role'] = 'client';
clientRejectData[clientId]['reject_text'] = data['reject_detail_map']['rejected_by_client'][clientId];
ticketData['user_reject_data'] = Map.of(clientRejectData);
}
} catch (e) {
DevMode.log("Error: $e");
}
});
}
}
}
The problem is the ticketData['user_reject_data'] is always limited to 1 person, like the data from before next id is overwritten. So if there are 2 person rejecting the invitation:
User A reject as admin
User B reject as member
the data that i expect to be shown when printing the 'user_reject_data' are:
user_reject_data{
"user_A" : {his info}
"user_B" : {his info}
}
but i will always get only the user B data, like the user A is being over written. I guess there's something wrong with the way I add the data to the map. How to fix this ?