Better to check what Roaming settings are set on the HLR/HSS. Parameters like VPLMN Allowed, should be reviewed. For cross border cases like what you have described check if you can send data, e.g. MMS, Web surfing, etc..
Check if you are using a GRX. Most CSPs have moved on from the dedicated point to point roaming link.
VBR/ Wallis Dudhnath