Allah or God?
[The holy Quran 17:110] Say, “Call Him Allah, or call Him the Most Gracious (Rahman); whichever name you use, to Him belongs the best names.” You shall not utter your Contact Prayers (Salat) too loudly, nor secretly; use a moderate tone.
[20:8] Allah: there is no other god besides Him. To Him belong the most beautiful names.
So, Who is Allah/God/Rahman etc.?
[2:255] Allah: there is no other god besides Him, the Living, the Eternal. Never a moment of unawareness or slumber overtakes Him. To Him belongs everything in the heavens and everything on earth. Who could intercede with Him, except in accordance with His will? He knows their past, and their future.
No one attains any knowledge, except as He wills. His dominion encompasses the heavens and the earth, and ruling them never burdens Him. He is the Most High, the Great.
Allah has many other attributes too but several crucial attributes are mentioned in the verse [2:255].
So, Allah/God is the Creator of the Universe and everything (nonliving and living beings including human) within it. Therefore, as long as we are attributing correct attributes of Allah, we can definitely call Him God as per the verse [17:110].
The verse [17:110] clearly tells us, we don’t need to call Him Allah always; He has many other beautiful names. Personally when I remember God, I call Him Allah but that is my personal choice and satisfaction.