Being a Witch and being a Wiccan are two very different things.
Witchcraft is just that, a craft, that has to do with magical practices. You don't have to be of any specific religion to be a Witch. You can be Pagan, you can be Christian, you can be an atheist and still be a Witch.
Wicca, on the other hand, is a very specific religion with very specific beliefs and practices. It is not compatible with being Christian as Wiccan beliefs are very, very different from Christian ones. Sure there are some people who claim to be Christian Wiccans, but they are actually practicing a sort of mish-mash faith that is neither Wiccan nor truly Christian.
If it's simply witchcraft and magic you want to practice then stay with your Christian beliefs and look at Traditional Witchcraft instead of Wicca.