Weird behaviour with pageable on filtering

[vinimxit]

My Collection:

var $ = jQuery = require('jquery'),
Backbone = require('backbone'),
_ = require('underscore'),
Urls = require('../../libs/urls'),
services = require('../../libs/services'),
skuListModel = require('../../models/sku/SkuListModel'),
PageableCollection = require("backbone-pageable");

var SkuListCollection = Backbone.PageableCollection.extend({
model: skuListModel,
sync: function (method, model, options) {
options = _.defaults({}, options, {
readUrl: Urls.sku.list
});
return services.sync.call(model, method, model, options);
},
state: {
firstPage: 1,
currentPage: 1,
pageSize: 10
},

queryParams: {
currentPage: "page",
pageSize: "limit",
totalPages: this.totalPages
},
searchOnParameter: function (search_string) {
console.log(search_string);
return this.fetch({
data: {
search_string: search_string
}
})
},
parse: function (response) {
if (_.has(response, "metadata")) {
this.totalPages = Math.ceil(response.metadata.record_count / 10);
this.skus = response.records;
this.totalRecords = response.metadata.record_count;
this.currentPage = this.state.currentPage;
return response.records;
}
}
});

module.exports = SkuListCollection;

When i call it in the View

searchData: function (e) {
var self = this;

self.skuCollection.searchOnParameter(e.target.value).then(function (response) {

});

}

It appends the result with the current collection how do i solve this issue.