(man to woman)
My dear friend,
It is very disappointing and frustrating.
I do not know why I can send you sms but I can not receive the sms you sent me. You should go to the shop where you bought the phone or to Vinaphone and ask for explainations and help to check the settings. Maybe your sim card needs to be changed.
Ask them why you can not send sms abroad and how you can fix the problem.