What else would it be that you can think of? Botting would only make sense as thats what you've been mainly doing on your account. Maybe, this is the warning before the permanent ban?
JaGeX is milking in the most they can out of RuneScape so I would'nt be surprised with them doing this.
PS. A few months ago, JaGeX had players pay to get their banned accounts back so this is not impossible.
OR
if your account was members, the membership payment which you/someone had paid for was charged back from them?