Pagination with Remote Data for Combobox

Question

I am trying to load combobox with deleted data from SQL database, Here is Combobox code,

{
    xtype: 'fieldset',
    title: 'Busname',
    items: [
        {
            xtype: 'myCombobox',
            name: 'busname',
            forceNewStore: true,
            pageSize:10,
            queryMode: 'local',
            displayField: "description",
            valueField: "description",
            mapperId: 'busnamefetch',
            maskRe: /[A-Za-z0-9]/,
            forceSelection: true,
            emptyText: 'Select Bus',
            margin: '15px',
            triggers: {
                clear: {
                    cls: 'x-form-clear-trigger',
                    handler: function () {
                        this.reset();
                    }
                }
            },
        }]
}

I map this in a separate mapper file, as shown below,

{
key: "busnamefetch",
type: "dServ",
properties: [
    {
        "key": "namespace",
        "value": "Travelmapper"
    },
    {
        "key": "query",
        "value": "selectbusname"
    }]
}

and here

 {
id: 'selectbusname',
namespace: 'Travelmapper',
statementType: 'CALLABLE',
query: 'SELECT busname as description FROM BusTable order by busname limit 10;'
}

Now, when I try to pager in combobox, the paging toolbar appears and says that 1 of ... is shown like that, but the next page does not work, that I am missing, please help me here, I have gone through many examples, not could get.