Create a bold graphic t-shirt design titled "London Calling." The design features a stylized illustration of a classic red phone booth, characterized by bold lines and geometric shapes that give it a modern twist. The background should consist of a gradient that transitions from deep reds to blacks, creating a striking contrast with the phone booth. The text "London Calling" should be displayed in a bold, sans-serif font, centered across the chest, with a subtle shadow effect to provide a 3D feel. Utilize digital illustration techniques to enhance the vibrancy of the colors, ensuring the red of the phone booth stands out against the darker background. In post-production, apply subtle drop shadows and highlights to both the phone booth and the text to enhance depth and dimension. The final design should maintain a transparent background, making it an appealing choice for those who appreciate a modern take on an iconic London symbol.