Frustration on payment

I have sold my vehicle through Integra Motor Group.The contract signed with Integra stipulate a seven working day period for payment,from the day,"a buyers"payment have cleared,to me "the seller".My vehicle was sold and through a WhatsApp message,I have been informed that the buyer's payment cleared on the 18th of July 2018.I started counting the seven working day waiting period from the 19th of July 2018,thus the payment date should have been 27th of July 2018. During the week of the 30th of July to the 3rd of August I have been told that my payment is scheduled for Thursday the 2nd of August 2018 at the latest Friday the 3rd.Friday afternoon I got hold of the CEO/MD,who assured me the payment will be done on Monday the 6th of August 2018.Now the benchmark moved to the 7th of August 2018.What I don't understand is,you received payment from the buyer,went through the seven working day period,so why the frustrating delay to do your payment to me?