Hi MysticalMira,
Hmm, I'm not sure what would be causing that; who was the true ending with? I can check into a few things and see but difficult to discern what would cause that.
Let me know who you dated last and I'll check ( ^^)/ sorry about that.
Hmm, that is odd; I've not heard of this happening anywhere else and just tested it myself.
The bonus tab appears in the main menu, not the Hellphone. If this doesn't work, you can email me or contact me on Discord, and if you zip up your save file I can take an exact look at what is happening.
My Discord is Whitehand#3403 ( ^^)/
Email is sinfulwhitehand @ gmail.com