I'm a student and I work part-time for a medium-sized company. For one day of work, I earn around €90. Normally, I work 4 days a month, but in January I took 2 days off. Yet, my pay for this month was €660 instead of €180. This difference is too big to be a raise or a bonus.
I want to maintain a good relationship with my employer as I was lucky to get this job and I hope to keep it during my studies. So I sent an email asking if this could be a mistake. It's been over a week and I've received no response.
Should I send a follow-up or just be happy for the extra cash?