Betfair customer service

where can i send feed back .. The new betfaiR multiple section is pathetic 1) I CANT combine my bet with major league BASEBALL , volleyball , darts and other sports  2) the web site is getting bad to worse ...CAN U SEND MY MESSAGE AND MY FEED BACK TO THE CONCEREN DEPARTMENT .. THE WEB SITE IS WAY TO SLOW AND THE MULTIPLE SECTION HAS CHANGED AND IS GETTING WORSE .. PLEASE SWITCH BACK IF POSSIBLE.. THANKYOU