You can use Sestek TTS service. Sestek Text to Speech service understands text to generate natural sounding human-like synthesized audio. It is available in 25 voices across 11 languages.
It can also be used in place of speaker records when a quick change needed in the prompts.

Related Products: Conversational IVR 1 (NLP+SR), Virtual Assistant 2 (SR+TTS+NLP+Orchestrator)