Twitter ads API "GET /1/stats/accounts/:account_id" unauthorized access - twitter

Question

I am using postman APP for accessing GET request through TWITTER API. Though I am able to generate output through all other GET and POST request through OAUTH 1.0. But when I am sending the request through "GET /1/stats/accounts/:account_id" method, its generating the following error.
{
"errors": [
{
"code": "UNAUTHORIZED_ACCESS",
"message": "This request is not properly authenticated"
}
],
"request": {
"params": {}
}
}
I am using the following request : "https://ads-api.twitter.com/1/stats/accounts/:18ce53yh9sw?entity_ids=88hjg&entity=CAMPAIGN&end_time=2017-05-14T17:00:00Z&granularity=HOUR&metric_groups=BILLING&placement=ALL_ON_TWITTER&start_time=2017-05-05T15:00:00Z"
This is the most important GET request for me to get the campaign level data. Any other way around may be helpful.
UPDATE:
The following request is working for https://ads-api.twitter.com/1/accounts/:account_id
{
"request": {
"params": {}
},
"data": [
{
"name": "Wadi.com",
"business_name": null,
"timezone": "Asia/Riyadh",
"timezone_switch_at": "2013-05-21T21:00:00Z",
"id": "18ce53yh9sw",
"created_at": "2015-03-12T07:33:09Z",
"salt": "0f034423fa35f95e8efc844a25c4d7a3",
"updated_at": "2017-05-17T06:03:58Z",
"business_id": null,
"approval_status": "ACCEPTED",
"deleted": false
}
],
"data_type": "account",
"total_count": 1,
"next_cursor": null
}
Regards
Shree Kant