If you are looking for free supplemental materials to use alongside or instead of a paid Callan course, consider these highly-rated resources: 0;16;

Algunas páginas de recursos educativos ofrecen muestras gratuitas de los primeros niveles (Stage 1 y Stage 2), lo cual es ideal para principiantes. Estructura de los Libros (Stages)

New vocabulary is introduced and then repeated in subsequent lessons until it becomes second nature.

You are forced to answer immediately, which eliminates the habit of translating in your head. Constant Correction:

Accessible via the app, this area features sections for Question & Answer practice (with recording capabilities), auto-corrected Dictations, and grammar exercises.

Absolute beginner (A1 level). Focuses on basic vocabulary, present tense, and simple sentence structures.

Every mistake in pronunciation or grammar is corrected instantly by the teacher.