They are giving me some malarky about a minimum
earned premium of $125.00.

Read your contract. The insurance company incurred the same expense setting up
and billing your account for the week's coverage as if you had let the policy
run all six months. Such clauses are common enough, and if it is spelled out in
the contract you owe, you owe.

(I'll bet if you had a claim during the first week, you would have expected
full reminbursement.)