As a general rule, no contact should only be used as a last resort, and shouldn't be put into effect after every single disagreement. It is perfectly natural for couples to argue and to work their way through their problems. No contact should never be used to punish your ex, and it is unclear if this is why you have chosen to implement it.
Remember, no contact is all about helping you heal during the breakup process, after dialogue has ceased.
Without knowing more details about your breakup, it is difficult to advise you. You are only on your first day, yet are anticipating receiving a phone call from your ex. This suggests that you don't think the breakup is permanent.
If you are maintaining no contact for the right reasons, then my advice would be to stick to this. However, if you feel that you and your ex can talk through your differences, then this is usually the best course of action to take.