。
I'm sorry to keep troubling you every time.
Literal
Every-time trouble [object-を] causing apologize.
毎度 ('every time') is a formal/business greeting opener. お手数をおかけして is humble speech — お + 手数 ('trouble') + を + おかけして ('causing') uses the humble お~する pattern. 申し訳ありません is a deep formal apology. The whole phrase is a standard keigo set expression.