We rightly and importantly emphasise that the Gospel brings freedom - but what does that mean? We also say that we are called to service. How do we balance service and freedom? Perhaps the important word in the question is the word 'balance'. It seems to me that so much of life is about appropriate balancing. I am currently reading Walter Brueggemann's The Covenanted Self (Fortress Press, 1999).
Brueggemann makes reference to the Israelites being freed from Egyptian slavery - only freedom brought a whole new set of difficulties. He points out how - p. 24 - "Yahweh had consistently said, "Let them go, that they may serve me. Consistently the governing verb is "serve" (abad), "enter into my service". (Occasionally the alternative verb hag is used, "make a festival.") Yahweh never said, "Let my people go that they may be autonomous," or "Let my people go that they may enjoy unmitigated freedom." "That they may serve me" means to come under a sovereign command. Thus the "freed slaves" have a freedom that is a new servitude, under new commands and new demands."
So what is the service to which God is calling us? It is in such serving that we will discover freedom. That is how we get the balance right.