I created this list of reliable Usenet providers that offer free trials so you can test their service:
Newshosting (750GB Free Trial)
Payment is via Paypal or credit card. The exact terms are “Free Trial is over in 7 days or 750GB used, whichever comes first. Free trial is offered for new customers only, one per customer.”
TweakNews offers a 10-day unlimited free trial. This reliable European provider has it’s own Usenet backbone. Credit card or Paypal required.
Usenet.Farm is an independent Dutch provider. They offer 20 GB of free downloading. No credit card or other payment required, only an email address.