As noted by @Chalupa_Batman , PM makes it very difficult to downgrade your plan.
Check your Change Subscription and see if there is a plan that is less than your current $34 even if it is not the one that you want. In my experience, it may be possible that after you have changed your plan to a cheaper one, even a 4G plan if available, other plans may become available, possibly the one that you want, when you are at a new price level.
I made the mistake of upgrading from a $19 1 GB plan to a $29 20 GB plan. I realized that I was paying an extra $120 a year for gobs of data which I never used. By checking my Change Subscription regularly, especially during periods of sales, I changed my plan incrementally to bring my price back down. I'm currently paying $20 for a 3 GB plan and the $19 1GB is once again available in my Change Subscription. It is a painstaking process that took about a year. The alternative is to port your number out to another provider and then port back in. However, I have some referrals which help lower my monthly price. If I ported out, I would lose all of those referrals.
For example, here is a screenshot of some of the plans which are currently available to me now in my Change Subscription. You should note that the $23 4G 6GB plan now available to me is superior to the $24 4G 4GB plan currently available for new activations. PM is always trying to entice their subscribers to upgrade to more expensive plans.
