Hi Wendra

There are a couple of things in your code

1- You cannot call methods where the method name is prefixed by _ because those are like private or internal methods and Odoo check specifically for that before calling your method, so you are not calling the right method in your xmlrpc call, you are calling get_salesteam_filter_mobile and not _get_salesteam_filter who is the one that receive the user_id parameter

2- Your method for be able to be called needs a decorator responsibly for wear it with the api environment variables like db cursor and context. This decorator could be @api.multi or @api.one if your method is defined in the res.users model to no even need to define the user_id parameter because it will be bind it to self as a browse recordset, or @api.model for arbitrary data parameter like user_id for any other model distinct from res.user

3- You don't need to pass the value of self for your xmlrpc call since self is an automatic parameter for object class methods referring to the current object and also as I said before used by Odoo to bind recordsets and many other environment stuffs 

Hope this helps