Write a letter including:
– Explaining your situation
– An apology
– Express that you would be interested in the position next summer
Dear Mrs. Johnston,
I hope this letter finds you well. I am writing in regard to the lab technician position that I interviewed for last week. I know that I accepted the position after it was offered to me; however, unfortunately, I will not be able to fulfil this agreement. Due to unforeseen circumstances, I will no longer have the time available that I would need in order to satisfy the required hours for the position. I sincerely apologize for no longer being able to take on this position, not only for inconveniencing you, but also because I really wanted to gain valuable experience working in the laboratory.
If you can accept my apology and if there is still an available position sometime in the near future, I would very much like to take on a position in the laboratory, even if unpaid.
Thank you and take care,