Bottom of the bill discount on internet service

I called Xfinity to cancel my service because I would be switching to ATT. The agent I spoke with convinced me to stay by offering me a $35 discount on my internet service bill if I added a mobile line to my Xfinity mobile service. The discount was called" bottom of the bill". So I agreed to stay and I added a new mobile line priced at $30/month and upgraded my current line to $30/month unlimited data. Since I have made these changes in late April, I still have not been credited the discount on my internet services. I have called numerous times to resolve the issue, yet my bill still does not reflect the discount. I was told it could take up to 60 days for the bill to reflect the discount. It has been well over 60 days. It is now the end of July. An agent was polite enough to manually credit my  bill due in July. My bill due Aug still does not reflect the discount. I will be calling Customer service again. I would not recommend adding a mobile line to receive the internet discount. It has been such a hassle, although it is a regular ongoing promotion that I have seen advertised in the Xfinity mobile store.