Change
We encountered some unexpected expenses, however, we decided not to
increase our fee.
To
We encountered some unexpected expenses[; h]owever, we decided not to increase our fee.
Or to
We encountered some unexpected expenses[.
H]owever, we decided not to increase
our fee.
Comma splice: Two complete sentences incorrectly spliced together with a comma,
rather than separated by a period or semicolon. A comma splice is one of
the most common errors in on-the-job writing. Comma splices frequently
occur with the adverbs however and therefore.