title: Currency and interval fields must match across all plans on this subscription. Found mismatch in interval field
body: <p>I am using stripe to implement payment feature. In payment feature I have two subscription plan monthly and yearly respectively. From stripe dashboard I created product and under that created two plans monthly and yearly. As per the name I set interval to monthly and yearly respectively. </p>
  
  <p>I am successfully able to create subscription. But when I try to change my subscription plan I am getting this error: Currency and interval fields must match across all plans on this subscription. Found mismatch in interval field.</p>
  
  <p>Error saying that currency and interval must match. But how can I make them same. For monthly plan I set monthly interval and for yearly plan I set yearly interval which is proper I guess. Don't know where I mistaken.</p>
  
  <p>Here is my code:</p>
  
  <pre><code>const subscription = getSubscription(req.body.subscriptionId);
        subscription.then((value) =&gt; {
          id = value.id;
        })
          stripe.subscriptions.update(
            req.body.subscriptionId,
            {
              items: [{
                id: id,
                plan: req.body.planId,
              }]
            },
            function(err, subscription) {
              if(err) {
                console.log('error .... ', err);
                return;
              }
              console.log('updated subscription... ', subscription);
            });
  
  
  async function getSubscription(subscriptionId) {
    return await stripe.subscriptions.retrieve(subscriptionId);
  }
  </code></pre>
  
  <p>I took this code from this: <a href="https://stripe.com/docs/billing/subscriptions/upgrading-downgrading" rel="noreferrer">https://stripe.com/docs/billing/subscriptions/upgrading-downgrading</a></p>
  
  <p>Please help me out.</p>