Vodacom ignores response on confirmation SMS.

Vodacom sent me an SMS with new contract details, which I decided I do not want. The sms states: Dear Sucker! We have received your order: Device Name: No Device. Provisional Contract Date Start: 30/06/21. Provisional End Date: 30/06/23. Monthly subscription R54.99 excluding any value added services. Please select one of the options 1. Accept 2. Change Deal 3. Reject

I selected 3 to reject and they responded with: Your response in Invalid. Kindly retry and send the correct response (I kid you not, their statement says 'response in Invalid' not 'is Invalid').

Anyway, I selected 3 again, their response: You have reached maximum no. of attempts. A consultant will be in contact with you shortly

My question is, why give me the option to select a different response than "1-Accept", if your system doesn't accept any other value? Why bother to send the SMS in the first place, if 1-Accept is the only value you expect as response, regardless?