If you purchase a plan you most certainly can keep your existing number! To do so, login with your existing TextNow account to purchase a device and/ or a plan from us.
By 'convert to a real carrier' are you referring to accepting verification codes? Our wireless accounts do accept verification messages via short code from third-party apps and services.
However, some can be selective with the wireless numbers they accept. If you're having trouble receiving verification from any app or service, contact their customer support to request your TextNow number be added manually to your account with them.