1. A computer-implemented method, comprising: creating, responsive to determining to transition a voice call from voice communications over a voice network to streamed text over a packetized data network, a voice conversation correlation identifier that identifies the voice call and specifies incoming and outgoing streamed text data as part of the voice call; converting additional outgoing speech spoken by a user associated with the voice call to streamed text data; sending the streamed text data identified by the voice conversation correlation identifier within an outgoing text stream over the packetized data network; receiving streamed response text data identified by the voice conversation correlation identifier within an incoming text stream over the packetized data network; and converting the received streamed response text data within the incoming text stream to speech output as part of the voice call; where receiving the streamed response text data identified by the voice conversation correlation identifier within the incoming text stream over the packetized data network comprises one of: receiving text advertisement content within the received streamed response text data within the incoming text stream associated with a subject matter of the voice call and rendering the text advertisement content during the voice call; or receiving text represented in a different language from a language spoken by the user and performing a language conversion of the text represented in the different language to the language spoken by the user, where the received streamed response text data converted to the speech output comprises the language-converted text.
5. The computer-implemented method of claim 1 , further comprising: analyzing a subject matter topic of the voice call; selecting advertisement content that corresponds to the subject matter topic of the voice call; and inserting outgoing text advertisement content of the selected advertisement content into the outgoing streamed text data.