“O you who believe, repent to Allah with sincere repentance” (Qur'an 66:8).
A general command to believers to repent indicates that people retaining the name of faith can commit wrongs requiring genuine repentance. If every disobedience necessarily terminated faith, the address would be interpreted quite differently.
The need to repent, the gravity of an offense, and the possibility that the original faith remains are not mutually exclusive. The verse supports responsibility rather than complacency.