Dealing with minor mobile carriers when distributing links via Qualtrics API custom code

Hello,
My organization has developed custom code to programmatically distribute Qualtrics surveys using the API. However, we've encountered issues with mobile customers using non-mainstream providers (e.g., MetroPCS, TracFone) because the domains can change and/or messages just don't seem to go through in all instances. Wondering if anyone else can assist. Specifically, we purchased a phone and mobile plan with MetroPCS and have confirmed receipt of SMS links sent by our program, yet we have had study participants report they have not received links. Does anyone have expertise with dealing with these different domains?