i am getting these text messages i get them 3 at a time all with the last 3 didgets in the no diffrent

My daughter has been getting txt messages from this number and 447802005734 for a couple of weeks.  The message is a gibbeish collection of letters. She is dealing with the sudden death of her husband and can do without this.  Does anyone know how to block these on O2?  Any help would be greatly appreciated