seems like a solid option for what you're after.
0.5¢/minute PAYGO, or monthly minute packages at 75¢ for 250 minutes, $1.60 for 800 minutes, or $5 for 5000 minutes (easy to unsubscribe from without closing the account). No requirement for purchasing a DID phone number, some of the better voice call quality you'll encounter at this end of the price spectrum (and far better audio quality than any free service), pre-configured apps for Android/iOS for use over WiFi/mobile data, can be used from any computer with speakers/microphone using their desktop app (Windows/OSX), SIP phone friendly account credentials (if you need that sort of thing - opens up usage on other smartphone and desktop platforms, etc.), and you can actually set outbound Caller ID on the account to use your existing mobile phone number so nobody knows the difference.
If you're on Ting's GSM coverage and don't need to roam off of the T-Mobile network, you also might be interested in giving US Mobile
a look. If you're on Ting's CDMA coverage and don't need roaming off Sprint, give Twigby
a glance. You ditch trying to harmonize prices between T-Mobile and Sprint wholesale as well as roaming rates, and the cost drops a fair bit... especially if you've only
got one or two lines on the Ting account.