People Outside of T-Mobile Not Receiving My Texts

I have been having the same issue for about a year or so. I thought it was my phone bc I had a Huawei pphone. So I purchased a Samsung z fold 4 this past March 2023. It did not fix the problem. I spoke to someone from T-Mobile, and they told me it's the other people's phones. I find this hard to believe, as I am the common factor. I am trying to purchase a house and my realtor does not receive my texts. I have to email him my responses. He is working with another fellow who texted me, I responded, he never received it so he called me to say I texted you. It's frustrating. I run a business and I never know of my customers (new and current) didn't receive my text until after the fact.