Please help this is important!!! About texting and calling

so problem started about 4 days ago i started to notice i cant text one specific person on whatsapp then i sent sms also thst person didnt get sms then i called that person and in middle of 1st beep it said user busy then i called from another pjone and that person said that he hasnt blocked me and also i cant message her on messanger please please help!!!