Calling international landline with Skype, Viper ,,,,

In the past I have been using Skype the few times I called international landlines. Now I am having a problem topping up my Skype-account. I downloaded Viper as an alternative and was able to do some top-up on that app (hence no issue with the credit card), but not successful in actually calling the landline. Anybody having any recent success in calling international landlines with any of these tools … or am I just missing an obvious alternative tool?

Skype works fine for me

Unfortunately, Skype has retired their credit system. The only way to make calls now (once your credits are used up) is to buy a minute or flat-rate package…

That is exactly what I have observed, and not only in Taiwan.

As for alternatives - any suggestion? Viper allow you to pay but not to call …
perhaps need to be behind a VPN?