I need help with the pre-payment

Basically, I decided to test the 300 free credits that Google Cloud gives.
But I can’t make the initial prepayment because the code arrived as Dl *Pln, and I don’t know what to do.
I don’t know if the $300 is already working or not, and I’m afraid of being charged without knowing I was spending money.
I tried to make the payment several times and receive new codes, but nothing arrived in my bank account.