Delete sender-id using delete method under your account
http://portal.thundersms.com/api/v2/
Note: Few elements in the endpoint may change from service to service.
{endpoint}sms/senders/{id}
Replace the {id} with the actual id of the sender that you would like to delete.
curl --location --globoff --request DELETE '{endpoint}api/v2/sms/senders/{sender_id}'
{
"status": "OK",
"code": 200,
"message": "Deleted Successfully",
"data": []
}