The ramban doesn’t say that the mitzriim did so independently; he aays that they went beyond the gezerah of avdus, but there obviously is a new gezerah, which they submitted to of their own volition.
Want mekoros? Sefer hachinuch on lo sikom; you can’t take revenge because everything that happens to you is min hashomayim. It’s all over shaar habitachon in chovos halevavos. It’s in basically every machshave sefer of the past 500 years.
See sefer sifsei chaim from rav chaim Friedlander, who famously reconciles the sources which seem to say that a baal bechirah can affect others. It’s a beautiful piece.
And it’s pashut sevara; why would bechira allow someone to interfere with what Hashem wants to happen?
And that’s just for yechidim; how much more so for klal yisroel.