StageWave supports up to 16 phones connected simultaneously, remember that the price is different for each number of connections, you can check it on the Pricing page.
It should also be taken into account that for 10 or more connections a good performance computer is necessary, this must have an i5 processor of at least seventh generation or equivalent. In the same way, you must have a high-performance router, you can see some recommended models in the "What router do you recommend?" article.