är det okej om jag ska lägga ordet "att" före ringa dig. sorry for my broken swedish
Yes, that also works.
Ringa vs ringa upp?
There are overlap, bit I'd say "ringa upp" is more focus on dialling and initiating a call, and "ringa" the whole thing with the conversation.
I am sure in English we would say "i tried to call you". Sounds weird with 'have'.