I have got a trial account on Twilio with a free number. When I send an SMS through the Rest API I do receive the SMS, but from a different number than the one I have been assigned.
Is this so because of the trial? Will it be fixed when I upgrade my account?
I need the users to be able to reply back with the message to the same number they received the SMS from.
Twilio developer evangelist here.
My guess is that you are sending messages to a country that doesn't support maintaining the original sender ID. I see from your profile that you're from Pakistan, you can check out the guidelines for sending SMS to Pakistan here.
As you can see from the support table, we can't guarantee that your Long Code (that is the phone number) sender ID is preserved and Two Way SMS is not supported.
So, this is not due to your trial account, but limitations with sending SMS messages into Pakistan.