BRITISH AIRWAYS - You need a lesson in customer service!!!!!!!!!!!!!!!!!

Could someone explain to me why they charge you to book a specific seat and then just freely change that seat anyway to suit themselves????? This is disgraceful that you charge people extra and then do your own thing - AND THEN - try and navigate their website to contact them - well, I;d be 100yrs old by the time it took me to a use able /user friendly website ! - no wonder your customers end up on HELLO PETER - perhaps you will take note now!