Elixir Error handling for sending request - Http 403 Forbidden

In my App, I am using a library TextLocal, where they are sending a get request to their site to send mobile OTP to my APP.

Below is the code which I am using

try do

	mobile = user.mobile

	sms = 
	    "<#> #{otp} ! is your verification code. #{hash_string_prod} "

	if sms == nil, do: throw(sms)

	errors -> "otp verification failed"

95% of the times it is working fine. But sometimes when there site(TextLocal) is down or some other reason I am getting this error in my mobile APP

“Http 403 Forbidden”

How can i catch this error properly and display a user friendly message like. Please try again after some time.
I have used try and throw method is there anything i am missing?