Grief is proof that relationships can outlast physical access.

A relationship is not only made of contact. It is made of understanding, obligation, argument, affection, and shared history, and none of those disappear when the phone calls stop. What you had continues to exist, changed in form but not deleted. That is why people speak to those they have lost and do not feel foolish doing it.

If it helps, keep the relationship rather than only the memory. Talk to them, keep their birthday, maintain the argument you were having. That is not denial; it is continuing something that has not actually ended.