Not able to send sms(Text messages) through api to USA region using csharp dotnet

We are actually trying to send sms(text messages) to US destination{.AmazonSimpleNotificationServiceClient}. from oregon region (Us west-2), in api call its showing successful but in aws console it shows failed. But we are able to send sms to mobile form mumbai region (APSouth) region using same api service. so all i got to know is we need an Origination ID to send sms txt messages to US destination. while requesting in excess limit it show only 10dlc option but not short codes. So even while creating an origination ID also i am facing issue. I have increased the usage limit in oregon region also. Below is the code i am using in api

AmazonSimpleNotificationServiceClient snsClient = new AmazonSimpleNotificationServiceClient("access key", "secret key", Amazon.RegionEndpoint.USWest2); PublishRequest pubRequest = new PublishRequest(); // pubRequest.Message = message+ " is the OTP for your multi factor authentication.This code will expire in 10 minutes."; pubRequest.Message = message; pubRequest.PhoneNumber = mobileNo; // add optional MessageAttributes, for example: ////pubRequest.MessageAttributes.Add("AWS.SNS.SMS.SenderID", new MessageAttributeValue ////{ StringValue = "clicinsight", DataType = "String" }); // pubRequest.MessageAttributes AWS.SNS.SMS.SenderID"] = new MessageAttributeValue { StringValue = "...", DataType = "String" }; //pubRequest.MessageAttributes AWS.SNS.SMS.MaxPrice"] = // new MessageAttributeValue { StringValue = "0.50", DataType = "Number" }; pubRequest.MessageAttributes AWS.SNS.SMS.SMSType"] = new MessageAttributeValue { StringValue = "Transactional", DataType = "String" }; PublishResponse pubResponse = snsClient.Publish(pubRequest);