Switching to portrait mode - i dont know where can be problem , my is fast (suggestion : after two days phone fill-up swap space more then is necessary , i have changed swappiness from 100 to 60 ,and its ok )

For missed calls - Using EDGE connection ?
If yes , this is not phone problem , but technology.
EDGE have same canal for data and voice ,so can't do both in the same time. (solved in 3G)