I use Tesco app for years and call quality is just fine, as all SIP providers offers. Better quality on Apple iPhone, worst on Android. But I ca't complain as never paid for calls, as when £1 finishes, I just register new number and have £1 again, plus free calls to landlines.
Sorry cold from me, a betamax service called freevoipdeal is just over a euro a minute and you get 120 days free landlines and and this is crucial it's a sip service so you can use the best android app which is csipsimple, the call quality thru Tesco's app will be garbage as are all these other internet calling apps because the app is resource hungry. Cold from me
Then your point is incorrect. You can join the service and Tesco give you £1 worth of credit, and this lasts for 180 days. Therefore you do not need to topup at all. You can simply let it lapse after the 180 have gone by.
My point is, it isn’t free when you need to top up £6 to get the free calls. That needs to be made clear in the title.
I just register new number and get £1 free :) Doing this for over few years and enjoying free calls.