Online purchase bad service

I ordered items on line all went well successful until i am suppose to receive my order. I got an email saying some of the items are cancelled due to lack of stock/damaged item which is not clear what exactly the issue is because they are saying or. Question is how do you say lack of stock if the items were processed successfully and paid. This is very suspicious and I am not happy with the whole process. I have been shopping online since 2012 I have never experienced such a service. it is first with TFG :(