Elias here with Shopify Support. Thank you for reaching out!
I understand you don't remember your old routing number, as a result you aren't able to change the bank account on file. I'd be happy to assist you with this; however, it may be worth noting that due to a higher volume of support requests at this time, it may be faster to get your old routing number directly from your bank. Would you like to give that a try first?
If not, we can move forward with the next steps and request our Accounts team to help with removing the old bank account on file. If you prefer to speak over the phone, you can request a callback or join us in a live chat directly on our Help Center. Simply log into your account and you'll be prompted to search a topic. After you've made a search, a 'Get support' button will appear near the bottom of the page. From there, you'll be presented with various options for contacting our live support.
That being said, I'd also be happy to help you over the Community Forums. For this reason, I've located your store and sent an authentication email to the registered email we have on file. Please check your inbox/spam folders and reply to it. Once we've verified your account, I'll be able to send this request up to our Accounts team.