PS Plus vita question

I got a good bit of credit left from my $50 psn card and was thinking about getting ps plus. I've been told that a credit card is required in order for me to even activate it. I have some trial codes that I can use but I keep getting told that my credit card will be needed. The whole reason I got a psn card was so I don't have to put my credit card in.

I couldn't find any info on the playstation forums about this. Does anyone know if I can use the credit to buy plus or even use the credit in case I want to purchase something. I can just go to a store a buy the 3 month card if I need to. If psn is going to charge me, i'd rather it be my psn pre paid card rather then my credit card.

Correct, if you use your PSN credit, you do not need to use or input your credit card for anything, including PS Plus. I have never entered my credit card on the PSN store or XBLA as I do not want them to store my info on their servers or for them to renew a membership without my permission, but I have bought a ton of content on both using prepaid cards.

You do not need a credit card to get PS+, you can use your PSN credit that you buy at retail. I don't know if you can use PS+ trials without a credit card however.