Hi @Pauline39, hosts here in the forum don't (not surprisingly I guess) have access to account information or details of payments. You'll have to contact AirBnB and the methods and numbers are here.
Go to your transaction history page in dashboard-account. is it in complted transactions or future.? what the the date on your first payment, because that will be be the date on your next payment, not the first of the month. you can call airbnb at 415 800 5959