I have seen it written wanna, which is what I would tend to use and also wonna.
我看到它写成 wanna,这是我倾向于使用的, 也是 wonna。
英语百科
Wonna
Wonna[ˈvɔnna] is a village in the administrative district of Gmina Biskupiec, within Nowe Miasto County, Warmian-Masurian Voivodeship, in northern Poland. It lies approximately 10 kilometres (6mi) north-east of Biskupiec, 17km (11mi) north-west of Nowe Miasto Lubawskie, and 73km (45mi) west of the regional capital Olsztyn.