Configuration using `runtime.exs` does not work

[walu-lila]

Describe the bug
When using runtime.exs to configure the package, sending sms fails with the following error
{:error, %{message: "The supplied authentication is invalid", status: 401}}

To Reproduce
Steps to reproduce the behavior:

1. Go to runtime.exs file
2. Move configuration from dev.exs/prod.exs to runtime.exs
3. Try sending sms
4. See error

Expected behavior
Sending of sms should still work as before when the configuration was in prod.exs