Pathetic pick n pay app

Very bad service from the customer service regards to my pick n pay asap i have been calling emailing the support group but no one is helping vert pathetic its been since 22 December i cannot buy from my app the error in my cart reads R NAN If i click on it then i get kicked out dont know what the hell this is i have credit on my app i want to use. Seems they just want to take your money and dont want to help people. I urgently needs this to he resolved