SMS (texting) provider options in the US

We use Knack, Make (Integromat) and Text Magic to send text messages to our employees and vendors. The applications work well together using a variety of triggers and it is no code, yeah! With Text Magic we use a pay as you go plan that costs $0.05/text. As the app has grown so has our # of texts and the costs are starting to get pretty high some months.

Has anyone used other providers for texting and if so what are the operational costs for them?