Now might be a good time to add an extra layer of security to your Instagram account. As previewed in August, Instagram has switched on two-factor authentication using apps like Google Authenticator and Duo Mobile, promising a more secure sign-in process than receiving a text message (an option since 2016). You can enable it by visiting the Privacy and Security section of the mobile app's settings, choosing Two-Factor Authentication, and then toggling the Authentication App option. Instagram can scan for compatible authenticators on your phone or invite you to download one.
The app-based approach offers one key advantage: it prevents the use of SIM hijacking campaigns to steer authentication text messages to another phone. Here, you'll have to be using a specific device to either answer a prompt or obtain the right code. This still won't make your account bulletproof, but it could discourage 'casual' intruders from trying to break in.