EE contract

My eldest and his misses have a contract with EE. Both have P30 lites his misses phone works fine full signal in the house 4g access my lads phone you can very rarely get through to straight to answer phone (he can’t phone out) he can’t use his data so has to hot spot of his other halfs he has been in contact with EE who have said it must be a problem with his sim tray but won’t do anything about it. He contacted Huawei who told him it wasn’t a sim tray problem as the phone was registering on the EE network so he needs to take it up with them. Long story short EE keep fobbing him off I’ve told him to return the phone and cancel the contract as they are not providing the service he signed up for and is paying for as the contract is with them it is down to them to sort the problem. Am I right on this one?