How do i call on landlines and phones if i get the subscription for unlimited calling all over the world

Skype Unlimited World subscription is actually limited to some selected countries and phone types.

Calling Offer Terms (skype.com)

If you e.g. trying to call UK mobile numbers, then these numbers are not covered by this subscription. Only UK landlines are covered.

But it says mobiles and landlines and I can see the name UK in the list of countries covered

Yes, you can see UK in the list of the included countries, but only as landline phones.

Both landlines and mobiles in Canada, China, Guam, Hong Kong SAR, Puerto Rico, Singapore, Thailand and United States

Only landlines in Andorra, Argentina, Australia, Austria, Belgium, Brazil, Brunei, Bulgaria, Chile, Colombia (excluding rural areas - LEX), Costa Rica, Croatia, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Guadeloupe, Hungary, Iceland, Indonesia (Jakarta only), Republic of Ireland, Israel, Italy, Japan, Korea, Latvia, Lithuania, Luxembourg, Malaysia, Malta, Mexico, Morocco, Netherlands, New Zealand, Norway, Panama, Paraguay, Peru, Poland, Portugal, Romania, Russia, Slovakia, Slovenia, South Africa, Spain, Sweden, Switzerland, Taiwan, Turkey, United Kingdom, and Venezuela.

Calling mobiles is only possible in Canada, China, Guam, Hong Kong SAR, Puerto Rico, Singapore, Thailand and United States