fix bug

server/controllers/GPS.Settings.js

@@ -11,8 +11,8 @@ module.exports.setFee = [
     const { amount } = req.body
     const fee = await Settings.findOne({ title: titleKey })
     if (fee) {
-      Settings.amount = amount
-      await Settings.save()
+      fee.amount = amount
+      await fee.save()
       return res.status(200).json(fee)
     }
     const newFee = await Settings.create({ title: titleKey, amount })