Not able to add 5g internet to my account

About a month or 2 ago I tried to get the T-Mobile internet plan through with an over the phone rep. It was available in my area at the time. Now I have an old plan  called the Simple Choice Promo which has been grandfathered in. I have been with T-Mobile for over 10 years. I never had a credit check and have missed out on several promotions because of this. My credit is not good but my bill is always paid and I like my plan. I was told during attempted setup the credit issue should not be a problem nor would I need to change my plan. However several reps said they could not find a rate for me and therefore could not set up my plan. they told me to go to a store. They believed they could do it. However I would have to pay an activation fee at a store . So much for the risk free trial. If it doesn't work I'm out the activation fee. I get it if the company doesn't want to take risks or can't back up what they said so they pawned me of to a retailer. No doubt they would not have been able to set me up because the last time I dealt with a retailer I couldn't get a phone upgrade without a credit check and a new phone plan. I would gamble on the credit check as long as I don't jeopardize my current plan and don't have to pay an activation fee.