where to find the b618-22d for rm4xx? thanks

guys, i 've been trying to change plan from digi 58 to i150. everything ok in the registration process but up to the transaction, suddenly transaction failed. tried already 3 different cards also can't. digi CS said call the bank. called the banks, cards have no issue (using debit card btw). then back to digi CS and they said try again in 2 hrs time. did that yesterday and problem persists. dunno what to do coz i tried again today, still can't