Why am I not getting an SMS on my phone in UK after it's been roamed and No service??

Ever since I entered UK in Oct 4, there's no MTN signal in my phone, I lived in uk and line has been roamed and about 4000 naira was paid to let my line to stay active yet i found it difficult to receive neighter sms/OTP..I have been trying to have an OTP to access my Gtbank app but OTP is coming upThis is the phone number: 0803 3818313 I even subscribed to roaming bundle twice , yet no MTN signal.I have suffered because of this, as I'm unable to receive OTP since then.I NEED YOUR ASSISTANCE.