Shield Compliance, a platform for cannabis banking released an open letter calling for the nation's leading card brands, including Mastercard MA-4.63%+ Free Alerts, Visa V-2.05%+ Free Alerts, Discover DFS+1.25%+ Free Alerts, American Express AXP+0.09%+ Free Alertsto reverse their policies of prohibiting financial institutions to offer payments services connected to their networks to licensed cannabis merchants. The news comes on the heels of several finance giants like Bank of America and Mastercard revealing they are lobbying…