Account blocked trying to make calls, apparently because I was using a vpn. Re-installed on a different phone with no vpn, using a brand new account. Still got "account blocked" trying to call. Tech support by chat not very helpful. Just got passed around and finally promised an email from the security team, which I never received. Wasted loads of time trying to fix this as I use Skype for business so expected a good service. Let down by uninterested support people. Used another app.