Best VoIP app for small business owners , what actually scales well?

VoIP apps are often marketed as all in one communication solutions, but real world usage can vary a lot depending on business size and communication volume.
Some small business owners prioritize simplicity and just want a reliable way to handle calls and texts, while others need more advanced features like team routing and integrations.
For those who have used VoIP systems over time, what has actually scaled well as your business grew? Did you stick with one platform long term, or did you eventually switch due to complexity, cost, or communication limitations?