Lost iPhone, can't access iCloud account..

We went to Mexico not a long ago and my mom lost her iPhone 6s. We couldn't find it at all so she bought an iPhone 7 plus but it couldn't be the same phone number as the one that got lost. She wants to access her iCloud account to get her pictures and notes back to her new iPhone. Unfortunately every time she wants to access her account, it asks her for a verification code sent to the lost number. She knows her password for the iCloud account but she can't get that verification code at all. It also does the same with her Gmail and some other social media accounts... if anyone can at least help us get in the iCloud account so we can also turn on the "Find My iPhone" and find her phone, we'd appreciate it a