Inconsistency

On the 24th of August I ordered from burger King, I've had many problems previously there was items missing I was refunded my full order amount, I then made another order on the 28th of August the same thing happened and now I'm being offered a partial refund now first of all why such a inconsistency in customer service or in your supposed policies if this not your drivers causing problems ,it's the restaurants and then your support staff really needs to be retrained on customer service as there is a massive inconsistency in service level