I understand your answer, for which I thank you. In part the fault is mine because I didn't realize I was buying something under the usual cellphone rules. But what I didn't mention was that the reasons I returned it were that: (a) our voice quality was so degraded that everyone who called us -- without exception -- commented that they couldn't hear us and any sounds were very tinny; and (b) it severed the connection to our home security system and essentially disabled it. This after having been assured by the local store manager that I wouldn't notice any change in service or quality.
So, yes, to the letter of the rules, they probably have me. But for a week's difference (21 days vs 14) I would have thought they might make an accommodation for a customer who has been with them for quite a while.