Will the wife be sinful if she pays the parking spot's rent from her allocated monthly allowance, despite her husband's refusal, knowing that she needs the spot to keep the car safe and to ease the hardship on her in raising the children, especially since the husband sometimes asks her to speak with men on the phone to sort out some matters?

The husband is not obligated to pay for his wife's car garage, and it is not permissible for her to take money without his consent, unless there is a mutual understanding between them. The wife is entrusted with her husband's money and is responsible for it; she should not spend anything except with his permission. The husband should not be stingy with his wife regarding her needs. There is no objection to women speaking with non-mahram (definition) men when necessary, provided Islamic guidelines are observed and there is no fear of temptation (fitna).