I changed phone numbers and discovered how many accounts still trust the old one

I kept my old phone number active for a month after moving to a new plan. I thought that was generous. It was barely enough time to discover how many accounts still used the old number for sign-in codes.

The obvious services were easy: email, banking, and the phone carrier itself. Then I found a retirement portal, a grocery-delivery account, a ticket site, a school alumni page, and an old payment app. Some let me update the number after signing in. Others sent a confirmation code to the number I was trying to replace.

Nothing has gone wrong yet, but the deadline has changed the mood. Once the old line closes, a forgotten account may become harder to recover. I also do not want a future holder of that number receiving messages meant for me.

I am working from evidence instead of memory. I searched my messages for common sign-in phrases, checked saved accounts in my password manager, reviewed important financial and email settings, and wrote down which services offer another recovery method. Where supported, I am moving away from text-message codes to an authenticator or hardware key, while storing backup codes securely. I am not removing the old number until I have tested the replacement path.

The hardest category is accounts I rarely use but would care about in a bad week: insurance, utilities, travel, tax records, and anything tied to identity. Those are exactly the accounts least likely to occur to me during an ordinary Tuesday.

What belongs on a phone-number-change checklist beyond the obvious logins? And how would you prioritize the last few days of overlap: by financial consequence, by recovery difficulty, or by how often the account is used?